I've got an 87 that had a 305 TPI, but spun a bearing, so replaced with 350 Truck engine. Kept the TPI, changed to 28lb injectore, 350 TPI computer chip, and adjustable fuel press. regulator. Car has been running strong for several years, but several months ago developed a hesitation and power loss. It began to get worse and if you reved it up under or not under a load, it would begin to break up after 2500 RPM. The strange thing is that it doesn't set the "check engine" light. It did something like this once before but it was much worse but that time the check engine light would act like a strobe light going off and on. So I changed the computer and all was ok. That was about a year ago. I changed out the computer again this time but that didn't solve the problem. I thought the coil might be breaking down so I replaced it and changed the fuel filter but no fix. Talked with a buddy and he said that acts like the fuel pump is pumping right pressure but not pumping enough volume. The car all but quit today, so I changed the fuel pump and no fix either. Any body got any ideas?

You might check the operating range of the TPS with an ohmmeter to make sure there are no holes(open spots) in the range from idle to WOT.
Check the seating of the EGR valve - possible leak.
Place a 150-200 ohm resistor across the unplugged ECM coolant connector to fake it into operating temperature to see if it smooths out.
Clean the throttle body inside the plates and where the IAC goes.
Tighten all intake and plenum bolts.
Ensure the intake hose between the MAF sensor and TB has no holes.
Unplug the MAF to see if it smooths out.
Base idle?
Base timing?

Does it have spark? Is it getting fuel?

Yes it does have spark and it does have fuel. It will idle fine and then when you go to give it gas, it starts to do its surging hesitation like its starving for fuel.

check the tps.......is it tuned port or throttle body?

He said its TPI and I'd add checking/changing the MAP sensor, the one with the vacuum hose to it and a 3-wire connector to it.
Plus check all hoses for their condition, if you think they are bad or have a question aboutthem, change them to remove doubt.

Its Tune Port Injection and my car doesn't have a MAP sensor, it has a Mass Air Flow Sensor which got replaced about a year ago. I'm going to check out the TPS, it seems like it might be the original one. I love the performance and fuel mileage of Fuel Injection, but when something starts to go wrong with it, it can just about drive you crazy!:)

tap on it while its running if the rpms drop i would suspect that...(maf)

If you eventually decide that the MAF is acting up, I'd do one more thing before spending $350 on a new MAF. Check the connector pins on the MAF. I've seen those loose their spring tension and corrode. After brightening up the pins with sand paper and tightening up the sockets with a pick probe, I was able to resolve a MAF problem on a TPI setup. Fortuntely for us, the parts store reluctantly allowed us to return the 2 MAF sensors we bought trying to fix the problem. Some parts stores won't allow returns on electronic parts.

I got the TPS off my car. It has 3 pins on it. Do you know which pins i need to ohm out?

The center pin is the wiper and the outer two are the ends of the TPS.

Try ohming the center pin to one of the other two. Slowly and steadily open the throttle while observing the ohm reading. Make sure the readings change smoothly with no glitches. DVMs with a linear bar scale in the display are handy for catching glitches.

checked TPS. Ohms go up or down depending on which pin you connect with the middle pin. The ohms go up or down smoothly, so I'd say that's good. Had ignition module checked out and it tests good. I'm gonna try and tighten pins in connector for Mass Air Flow Sensor and see if that helps. Someone told me to check the acutal fuel pressure. I don't think the pressure regulator diaphram is bad because there's no black smoke. It has an adjustable press. reg. on it. I believe I was told to set it for 43-46 psi with the 28lb injectors that I have. That is what the pressure should be when you turn the key on and the pump cuts on for a few seconds before you start the car, Right? What should the fuel pressure be at idle and at WOT? Also Everett#2390, you asked what the idle and base timing are. The base timing is set at 0 for the truck motor. 350 TPI factory motor is supposed to be set at 6 BTDC, but it was spark knocking so I set it at 0 BTDC to help with that problem. The idle is 500-600 RPM .

Fuel pressure at WOT should increase, say 8-10 PSI.
Your 28# injectors are big, but you said it used to run good on these.
Normal is 21#. I used 24# on one I had and it worked fine.

Appears TPS checks out okay.
I assume you are using the initial form the donor truck, and that's fine. Strange the ECM doesn't correct for knocking. Knock sensor good? Does it have one?
Base idle looks good.
You might install a 0-10 or 0-15 PSI gauge onto the exhaust sytem, remove the check valve on the manifold, and make a WOT run to see what backpressure reads. Should not be over 3 PSI. I suspect this might be happening as the EGR valve may be popping open with too much backpressure.

It's been at least 3 years since I changed the engine out. I'm pretty sure they are 28#, but they might be 24#. They came out of a 95 Camaro Z-28 with an LT1. I believe I was told they were 28#, but I might be wrong. The cat was replaced about 7-8 years ago, so maybe it's getting clogged up. Although it doesn't have that rotten egg/sulfur smell so I'm not absolutely sure. I'll check the back pressure on the exhaust this weekend and see what happens. I want to everyone who has given me a piece of advise. I surely apprecaite it!

Checking max fuel pressure can be done in the driveway, just remove the vacuum hose and watch the gauge increase. Being as it is adjustable, an aftermarket unit, there may not be a hose to remove.

Knock sensor work? Might not have a knock sensor since a truck engine, would of had to transfer from 305 - look above starter, pass side drain plug is knock sensor. Use timing light to watch marks and hit block with a hammer and watch the timing retard. Like I said earlier, surprised the ECM doesn't regulate timing. You should hear no knocking as ignition should self-adjust.

You also might take a look at the dist connectors because RPM Reference goes to the ECM and ECM splits it - IGN timing and INJ timing. If revving up and acts up, can you retard ign timing and the engine smooth out?