Engine runs rough after driving 30 no acceleration. Shut it off and restart it goes away but reoccurring in shorter periods of time. Replacing iac fixed it for about an hour. No codes new distributor tps wires plugs fuel pump fuel filter maf knock sensor new injectors o2 sensor nothing older than six months besides 4 prong temp sensor but that's $350 by itself can't keep throwing money at it got some pig tails to replace Tuesday hopefully just a connection short I run only premium gas as the problem occurs I will be doing 70 then it causes deceleration that progressively gets worse if u don't shut down the car and restart

 

You might have a cat going bad and stopping the exhaust flow.

 

No cats, egr delete, 62 mm throttle body, long tube headers, glass packs chipped and tuned, msd cap rotor, accel coil, morroso wires, accel header spark plugs, monster trans, 2400 to 2800 stall, aeromotive stealth pump, bbk adjustable fuel pressure regulator, accel 23lb fuel injectors, lunati cam, double roller chain, Tuned out was 186hp and 320 torque, ran great for 2years just don't want to play sensor game again, problem started developing over the summer, when in ran good would burn through all gears, this was a intermediate problem but becoming constant

 

Check the fuel pressure under load, when it is showing signs of no power. Possible problem with the Aeromotive AFPR. The Aeromotive LT1 AFPR is a major source of problems..... not sure if they have the same issues with the 3rd Gen engines.

 

I replaced that too the first one lasted me a year I was having issues after a bad gas situation what is a good brand if that turns out to be the problem thanks for input

 

GM parts are usually the best. Unless you want to run an elevated fuel pressure, there is no need for an adjustable. I run an outboard Weldon AFPR, to maintain 58psi (4 bar).

I'm not familiar with the details of the part you refer to as the "4 prong temp sensor but that's $350"..... what is it for? .... coolant, inlet air? I can't find anything like that on the Chilton 86 TPI ECM diagrams. For some reason, they do not have an 85 schematic for TPI.

Did you mean to type 52mm throttle body? I run a 58mm, and the shop that built my engine was able to show me on the engine dyno that I could have made the 496 flywheel HP (NA) with a 52mm TB. The 58mm TB fed all the air the engine could consume at only 77% open. They still laugh at my 58mm TB

 

The temp sensor was actually a two prong shaped like a injector pigtail been awhile since I looked at it Stock pumps typically only last me 3days to a week( Airtek )I'm kind of Leary about using a delco pump cause their made in China and I'm concerned about the quality the first aeromotive pump that I used lasted me a year so I can was looking for something of a better durability if that's possible like a Holley or something of that nature not so much for flow but the reliability of pump I believe I may have a short to ground somewhere that I have been unable to locate

 

Walbro is decent. Check the Racetronix site.

I run dual Bosch 205 LPH high pressure pumps. One of them is 15 years old (in tank) and the other (outboard off a sump at the bottom/rear of the tank) came with an NOS nitrous kit that I bought 20 years ago. They in tank install does require some adapters, and modification of the stock sending unit.

Of course, check the pressure under load before you do anything.

 

I know you said you replaced the distributor but the symptoms sound like the HEI control module heat soak problems.

 

Ok replaced fuel pump and reran power supply to battery(was hooked to alternator). Hopefully fixes it for good And I fixed a massive vacuum leak in the front bottom tubes on both sides (had gaskets reversed with each other ) now cylinders 5 and 6 are not firing. I have spark and rockers are opening and closing Is there a way to check fuel injectors without pulling them or a passage that connects the two that may be clogged