Your exhaust won't be the cause of your trouble. The ICM might well be though.... Not sure how available those are any more.

 

I'm mostly leaning towards that for everything I've read just matches up so well with what the truck is doing for that part, is is 27 years old and has almost 190k miles so I wouldn't be surprised if it's going bad, Ive been calling junkyards in the area to try and save myself from spending the 2-400 dollars on eBay which is the only availability it seems

 

Try car-part.com. They search a HUGE number of yards, and you can specify distance.... Maybe you can find a yard that will ship one to you.

 

Tried using a timing light to go from coil to coil while it was running to test for spark, even while running very off every single coil had the same consistent spark, so I'm starting to suspect a fuel or air issue, last I checked the throttle body it looked clean, all motor sensors were replaced within the last few years, new air filter, lines aren't clogged, age of fuel filter is unknown, would it be worth taking apart and cleaning the throttle body, maybe changing the fuel filter with my next oil change?

 

What spark plugs are in it? How old? Are you getting any misfires? (I don't trust the misfire counters on the 8.0, as I had a completely dead cylinder, plug wire burnt in half, and it never set a code.)

 

The misfire is what I've been chasing this whole time, plugs are new about 1000 miles or so, coils wires new within last 2 months, I assume injectors are original, I've been told by a shop I tried to have diagnose this issue that fuel rail pressure is good, no injector ping, but I don't know if they're all clean, it seems when I drop off the throttle after getting to above 2k rpm accelerating it seems to Jake break off a dead cylinder or 2 like it's lost spark or fuel to that cylinder, almost like something stops firing, occasionally happens while running power drops off like I'm dragging a cylinder

 

I'll add that when it starts running off, idles smooth, runs very rough especially when it gets into overdrive it shakes the truck bad, my dad has a 96, has no similar issues whatsoever just being a year newer, granted his has 80k less miles, and Ive almost ruled out it being the icm in mine because when it was misfiring, the separate coils controlled by that module all had spark, also sounds like it has combustion near the cat somehow

 

Sometimes, I get the impression that TCC doesn't unlock until you actually step on the brake. At least, it sure feels that way.... No idea if that is actually the case though.

Might not hurt to fun some fuel injection cleaner through it. So far as I know, the only fuel filter is on the pump module, IN the tank, and is not a regular maintenance item. It gets changed when the pump fails.

Also, on mine.... ONE dead cylinder was pretty much unnoticeable.... the engine still ran really smooth, and no issues in O/D. So, I suspect you have more than one cylinder acting up. Trouble is, without actual codes, we don't know which cylinders are the issue..... and I am unsure of a reasonable way to check for that. Even though I don't really trust them, I would be interested in what the misfire counters have to say, though, being OBDI, not sure the PCM even tracks that.

What TYPE of plugs are in it?

 

Sounds like it could be a vacuum leak. They have been known to start leaking at the back between the upper and lower intake. I would smoke check it and see if you have any leaks. Worth a try before throwing an ICM at it. Also does it use any coolant or oil? They aren't know for head gaskets but that doesn't me it couldn't happen.

 

They're ngk iridium plugs, no codes whatsoever and I dont think it's a spark problem, timing light ran consistently for every plug right off the coil pack so I'm not suspecting spark being an issue, and I agree with more than one cyl being down and it's just so intermittent it's hard to track, there is an in line fuel filter on my truck underneath the driver side door area, looks pretty old, I've run a couple tanks of teckron and seafoam through it, nothing really helped that's why Im thinking if it's an injector it's possibly getting lazy or maybe something with the intake is entirely possible