Sensor Problem diagnoses help!

I have a 92 K1500 5.0 L with 210k miles on it so its not a brand new engine by any means, but it is gutless! It has no power at all. Its so severe that when driving highway speeds(80 mph) it frequently downshifts like when going up a big hill, but its on flat ground. Now every now and then it runs like a champ and has plenty of power and get up and go and then the next time i drive it its back to the same old powerless pickup that it has been. So with that being said im thinking due to those circumstances its probably a sensor problem, the sensor every once in a while starts working and causes something to happen that is giving me more power but i dont know what sensor would cause this. I am thinking the O2 sensors but im not sure. It might not even be a sensor problem for all i know but there is definitely something wrong. HELP PLEASE!!!!

I have a 92 K1500 5.0 L with 210k miles on it so its not a brand new engine by any means, but it is gutless! It has no power at all. Its so severe that when driving highway speeds(80 mph) it frequently downshifts like when going up a big hill, but its on flat ground. Now every now and then it runs like a champ and has plenty of power and get up and go and then the next time i drive it its back to the same old powerless pickup that it has been. So with that being said im thinking due to those circumstances its probably a sensor problem, the sensor every once in a while starts working and causes something to happen that is giving me more power but i dont know what sensor would cause this. I am thinking the O2 sensors but im not sure. It might not even be a sensor problem for all i know but there is definitely something wrong. HELP PLEASE!!!!

92 5.0 L V8 is not no speed demon.
But
First step would be a first class AC-delco parts tune up.
With base timing check and fuel pressure test and cat back pressure test.

Any codes or check engine lights?

Believe me I know its not super fast but like i said mine is lacking major major power. I know a guy who has a 305 thats lifted and has 33s on it and its not terribly sluggish. I only have 235s on mine and its slower and has less torque than his pickup.
As far as what you said about parts and what not you mentioned fuel pressure test. The fuel pump is pretty bad when i took it out it was almost shot and i rescued it(didnt have the money at the time to get new one) So im sure the fuel pump isnt doing the greatest job. Could this be the cause of my issues? Also you said a first class AC Delco parts tune up. My question for you is what parts are we talking about here? My cats are almost new so they arent plugged for sure. Timing is in check because thats originally what i thought the issue was but that didnt help. Lastly every once in a while it throws a code for Electronic spark timing low voltage/Electronic spark control circuit problems, but I dont see how that would cause a lack of power as big as whats happening.

Just so you can understand how severe the lack of power is compared to when its running right....When running right getting on the interstate I can get up to speed and have my cruise control set at the end of the on ramp or a little after. When it runs like it normally does(gutless) It can litterally take almost a mile or more to get up to speed and then driving on flat straight road the tranny constantly downshifts from overdrive to drive due to the spedometer dropping below what my cruise control is set at. It will get up to speed shift back into OD and then 5 seconds later do the same thing all over again.

As far as a Good AC- Delco tune up goes.
Always Use the AC-delco plugs the Good AC Delco book calls far.
If a dist cap and rotor is needed use AC -Delco.
Always check base time like disconnecting the base time set wire and make sure the engine is set at base time.
Make sure it is working good with time set wire disconnected and check with wire hooked up for good advance.
If you have codes for spark control there is a problem there.
That may be why it is not running at full power.
I have run into a lot of problems with that setup.
From Knock sensors to wiring to Bad computers.

What is the code no you are getting?
If the same code comes back after code clear get a repair flow chart for that code and go threw it.
When it loses power does the check engine light come on or set a code?
Also on that year there is a lot of dist that have excessive side play.
Check and use a good brand air and fuel filters.
And always check running on the road fuel pressure.
What was the pump doing or not doing and what did you do to rescued it?
If a fuel pump is bad I know of no way I know of to fix it outside of a new good brand fuel pump .

As far as a Good AC- Delco tune up goes.
Always Use the AC-delco plugs the Good AC Delco book calls far.
If a dist cap and rotor is needed use AC -Delco.
Always check base time like disconnecting the base time set wire and make sure the engine is set at base time.
Make sure it is working good with time set wire disconnected and check with wire hooked up for good advance.
If you have codes for spark control there is a problem there.
That may be why it is not running at full power.
I have run into a lot of problems with that setup.
From Knock sensors to wiring to Bad computers.

What is the code no you are getting?
If the same code comes back after code clear get a repair flow chart for that code and go threw it.
When it loses power does the check engine light come on or set a code?
Also on that year there is a lot of dist that have excessive side play.
Check and use a good brand air and fuel filters.
And always check running on the road fuel pressure.
What was the pump doing or not doing and what did you do to rescued it?
If a fuel pump is bad I know of no way I know of to fix it outside of a new good brand fuel pump .

Its code number 43
When it loses power which is more normal than when it has power no codes come on or neither does the CEL.
As far as the fuel pump im not positive on that my dad pulled it out while i was away at school and when i came back he said it was almost shot but fixed it so it would work but it still wasnt probably right or going to last a while. I think it possibly had to do with rust and corrosion issues.

Its code number 43
When it loses power which is more normal than when it has power no codes come on or neither does the CEL.
As far as the fuel pump im not positive on that my dad pulled it out while i was away at school and when i came back he said it was almost shot but fixed it so it would work but it still wasnt probably right or going to last a while. I think it possibly had to do with rust and corrosion issues.

Code 43 can be caused by bad knock sensor or wiring and plug-in to them.
Also spark control module or bad computer.
To repair for that code you will need to get a repair flow chart for that code and go all of the way threw the repair flow chart.
I would also check fuel pressure and for cat/exhaust restrictions.
Like a back pressure test.

What is engine vacuum reading at idle and at 2K rpm?

Where can these flow charts be obtained from?

Where can these flow charts be obtained from?

Code repair flow charts can be found in any good repair informat program.
Factory repair manual or micchell on demand and all data repair manuals.
Also All data DIY online repair info subscription.

Thanks for your help ill go through the chart and see if that fixes my problems if not ill try a few other things and hopefully I can get my problems fixed.

Thanks for your help ill go through the chart and see if that fixes my problems if not ill try a few other things and hopefully I can get my problems fixed.

Good deal.
That good repair info is worth it weight in gold and can save you many dollars by not just throwing parts at it.
Go threw everything in it that pertains to your problem.
Good Luck and let us know how it goes.