95 GMC Sierra Problems... Stumped

[abstrakt123]

ok so firrst the basics
1995 GMC Sierra 1500
4.3L V6 4X4
5 speed Manual
168k miles

___PROBLEM___

so in the past few weeks i have not changed a single thing since the problem has arised.
i have already replaced the Starter, Fuel Filter,Air Filter, Spark Plugs, Water Pump, Every Gas Fuel up I use Seafoam or IsoHeet, new muffler (thrush pipes)
Symptoms.
-it only happens certain days sometimes just for a minute others. it will do it no matter what
-will start to sputter like its not getting enough fuel or bad spark but that wouldnt make sense if it occasionaly does it only sometimes. which made me eliminate fuel pump and spark plugs
- the sputter consists of massive loss of power even sometimes to the point to where no matter how much pedal u lay down it wont even make a noise until u floor the pedal and then it will kick and be totally fine...until you let off the gas again. i mean litereally no sound from the engine not even an attempt at noise( i have a loud muffler so u can always tell) sometimes when u let it try to recover it lets a huge backfire sometimes a couple before it starts moving again.
- somedays it will rough idle weather its warmed up or just cold. and it will sit there and fight with its rpm. starts to idle fine. starts sputter and dipping to low then revzs it self up,. comes to an idle and a few seconds after it will begin to start dipping over and over until it finally will just sputter and die. but it will start right back up everytime. its more of an annoying nuesence then anything

if anyone can help me at all on determining what could be causing this issue without sinking tons of money ( i dont have) to replace parts till i finally find the right one

my opinion.. its either of the following
-Mass airflow sensor
- distributer cap
-loose wire
- oxygen sensor
those are the only outcomes i see any ideas please please let me know i love this truck all to much to want to part ways and give up

_-Update. i have Replaced the distributor cap and Rotor and cleaned out the EGR valve as well and problems persist.

[maxwedge]

Is this a Cpi Vortec or throttle body?

[PaulCB]

you can try pulling the wire off the mass air flow sensor....this will put the comp in default. if the problem goes away its the maf sensor. The iac valve on the tbody gums up thats another possibility
i am leaning to maf though.

[phipps]

Pull the distributor and check the distributor gear for wear. I had issues with my 97 running rough and replaced the plugs, wires, cap, rotor and coil with no resolution of the symptoms. I did some research online and found out these engines had issues with the distibutor gears getting worn and causing the symptoms I was having.

After replacing the distributor the symptoms went away.