94 Sierra bogging down

I have a 1994 GMC Sierra 4x4 (non-Z71) w/5.7L TBI and it started hesitating yesterday while coming home. I talked to a couple local mechanics and they suggested replacing the fuel filter, so I did and it ran perfect last night and earlier this morning till I was cruising home @ 65mph when all the sudden the engine bogged down and started bucking. I managed to make it home doing a max of around 30mph. At home I take the breather off and notice that one injector is dripping at idle while the other is spraying. If you give it throttle they both appear to spray, but the engine will only turn about 3,000 RPM and bogs down really bad. All guages read fine (temp/oil press/amp) and there is no check engine light on, but it does work.

I'm assuming I have a dirty injector that isn't pumping enough fuel, but wanted to ask others advice before attempting any repair.

(I also had just pumped $20 of 91 octane gas about 10mins before this started, could it be bad gas, and how would I check for that?)

Any advice or suggestions are appreciated!

Low fuel pressure is the most common cause, or that injector could be bad, I would make sure you have 10-13 psi.

I replaced the distributor cap and rotor button with a decent priced Accel combo because they both were old and pretty corroded, but this didn't help the situation.

I'm now leaning toward the fuel pump or injector again as stated by Maxwedge above.

PS: I thought fuel injected vehicles were supposed to have alot more than 10-13 psi, more like 45...?

Edit: Please correct me if i'm wrong about the pressure, but i'd checked Autozone yesterday and the OEM replacement pump said 45psi rating.

Ok, here's another symptom:

I fired it up this morning after sitting overnight and it ran better than it's ever ran since i've owned it. (1yr)

Till it got warmed up, then it started hesitating and bucking a bit, so I came back home.

I'm assuming heat is an issue. I haven't changed the coil since i've owned it and it does look pretty old from just outside appearance, and was told that a failing coil will sometimes get weak when they get hot.

It's only a $20 part and easy to change, so I think i'm going to change it, but i'm strapped for cash kinda and hate to replace it if there's nothing wrong with it.

Also I added some Lucas fuel injection treatment yesterday before anything, and they're not spraying great, but a bit better than before.

Hopefully i'll be able to find a gauge to check my fuel pressure today and check that to see if that's still possibly the culprit.

A throttle body set up is 10-13 psi, I would also check the coolant temp sensor they were famous for reading cold temps when warmed up ,which causes performance issues ,it will run very rich.

UPDATE:

After replacing the cap/rotor/coil (which was needed anyways) and adding the Lucas fuel injection treatment, and some STP water remover through 2 tanks of premium gas, the problem is getting better and better.

My fuel pump is now ALOT quieter and has a more 'consistant' sound. Now it's more of a hum than a buzz that crackles now and then.

Also my injectors are spraying alot better pattern.

Maybe this will help someone that has an original 280k mile motor thats fuel system was neglected through the years. :)

In the future, when finances allow, I plan on replacing the throttle body, fuel lines, fuel pump, and also properly clean the tank, but until then i'll keep running a bottle of Lucas injector cleaner and some water remover every other tank.

Injector cleaner: $5
Water remover: $2
Figuring out this headache without spending a ton of time/money: PRICELESS.

Thanks for your well intentioned advice Max. :)