I need more diagnostic tests to check, throw 'em at me.

I have an '87 Formula 350, stock except for AFPR (48psi, diaphragm is not ripped), and headers with the EGR system removed.

The car runs fine for about 4 minutes, then starts misfiring (and also small "pops" like backfires), but when I floor it, it all clears out and runs fine until I let off the gas again, then it instantly(which is why I though it was electrical) bogs back down and starts misfiring again.

There is NO codes, but I still thought it was an electrical problem, everything has been replaced, distributor, cap, coil, wires, ign module, ESC module, plugs, MAF sensor, MAF power and the burn-off relay, ECM (but not the PROM), TPS, IAC, new heated O2 sensor, coolant sensor for the ECM. Injectors are 15-16ohms, and timing is at 6*BTDC

I have also datalogged and everything is within specs except it is running a little rich.

now just recently, I noticed gas is puddling on the drivers bank of the tpi manifold, and looks like it is coming from the 9th injector (from the housing).
wouldn't gas leaking out of the housing and the connector cause it not to work at all? (shorting out the pins)
would the misfires be causing backpressure and blowing pressure (gas) out the housing of the injector? but then wouldn't the brake booster blow?
also, it's only the 9th injector, shouldn't the car be running fine without it if it were the problem? I unplugged it and the problem still consisted.

most of all, how do you test injectors to ground? from the lead to the injector housing? or to the engine block? would testing it this way even tell me if they are bad? because the problem only happens after the first 4 minutes.

 

Sounds like you have a leaking injector or injectors. The cold start injector (9th) only operates when cranking. The puddling of fuel could be from the higher fuel pressure. Adjust it down to about 42psi and see how it runs. That is where stock pressure is in the range of. Also would need to change the seals to the 9th injector if they are leaking like that. Try this and let me know what you find.

 

would leaking injectors behave like that?

Thanks for the response, I'm going to tow it someplace where I can work on it Thursday, I'll remove the fuel rail with injectors and see if they leak. I'll reply back then.