How did you time the engine after installing the distributor and electronics

After setting number 1 cylinder on TDC install distributor with in the number 1 firing position. Making sure when fully inserted it is still in alignment. This is the first thing my mobile mechanic checked.

Are you positive the old engine and new engine have the same exact camshaft? If they don't, the ECU will need to be recalibrated.

That would not cause the issue he is having.

If you didn't put the ecu in base timing mode then set the timing then remove from base timing mode its not done correctly...........

If it has the flat cap , that is not the procedure. Lots of 350mpi’s have the flat (crab) cap. If it has the est/voyager dist, then your procedure is typ correct.

This pic is the flat/‘crab’ style

Btw, and again: 90psi is horrible.

Agree, ya I got BBC on the brain didnt mess with the mouse motors

do you still have your old spark plug wires?if so,put them back on and see if it revs up.I had a 350 that did something similar,turned out the spark plug wires were not seating in the cap,put old wires back in and up on plane we went.just a thought.

Joe,

When you try and throttle up, what does your exhaust output look like...?

Understand first that the TPS is essentially nothing more than a movement indicator. It does not tell the ECM what speed you want to be running, but rather, when you want to change speeds. The ECM commands fuel based on MAP and RPM. When you shove the throttle forward, the throttle blade opens, providing more air while the RPM and MAP remain essentially the same (for conversation's sake), so the AFR must be corrected momentarily with a shot of extra fuel. So, the TPS commands "acceleration enrichment". I'm going to assume the same process, in reverse, occurs when you back off the throttle (I am a total layman, who has learned a few tidbits through osmosis, being in proximity of an EFI genius working on my engine's tune).

So, after rebuilding my 496 last winter, where I replaced the PCM555 with a Holley HP, we noticed a drastic increase in fuel consumption. As in, WAY more than any predicted gains in HP we expected from the various improvements we implemented during the rebuild to have incurred. Having full access to the tune via Holley software, the tuner was able to discover a LOT of electrical noise coming from the TPS, which was triggering acceleration enrichment, pretty much constantly. This was the primary culprit for the excessive fuel consumption, as well as some minor behavior gremlins we couldn't seem to tune out. After installing a new TPS, the problem initially seemed to be resolved, but then it returned. Not as bad as before, but still remained. The tuner pulled the connecter and discovered the retainer/locator sleeve on the connecter had been lost, so the connecter, while firmly clicked into place, was not securely tight; it could be wiggled. After correcting this issue (spliced in a new connector over the winter, while we had the engine out again to address a coolant leak and swap a cam, etc, etc...), and after first fire this year, the electrical noise is gone.

Long way around to get back to your engine's behavior gremlin going away when you disconnect the TPS.... In many cases a bad signal is far worse than no signal at all. Without the TPS, the ECM is just going off the fuel table, and it's just winging it through throttle changes. But a TPS throwing a bunch of noise will cause your accelerator pumps to have a field day. Ensure all connections are positive and secure and see if you can find a way of detecting said electrical noise. On the Holley, it was easy. The tuner could just look at a graph of the TPS signal output. It should have been a nearly flat line that smoothly followed my throttle sweeps. Instead, it looked like a crackhead's EKG. This sounds a LOT like where you are.

Something to chew on.

Thanks. Brad.