Thread: Ford EFI conversion problems/backfire,miss

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Has anyone run into this problem? I just did a stock EFI conversion on my 5.0 ford I used all stock ford parts to do a conversion and have this problem with the motor backfires through the throttle body and misses and seems to flatten out at around 2800 rpm and generally seems to fall on its face above this rpm. I have replaced all sensors : CTS,ATS,O2 sensors, Throttle Positions sensor, and the distributor also the cap rotor , plug wires,plugs and even a new computer A9L also i replaced the fuel pressure regulator with a new one and checked the pressure it checked out at 32psi running 39psi key on, I took it to a mechanic and he kept it for 2 weeks and replaced all these parts and it still wont run right!! I used a wiring harness from an 89 Mustang donor car and went to Fordfuelinjection.com and followed all his instructions on the swap which was very helpful with getting the harness stripped down to the bare minimum of wires that would be used, yes I have a good ground to the computer and the O2 sensors ,the motor runs great below this rpm and if it were being driven by my mother you probably wouldn't even know there was a problem sense the motor idles fine . Oh did I mention the motor has a B303 fordmotorsports cam in it. other than that the motor is stock crate motor 1993 model the timing is set a 10' btdc with the spout connector out with the spout connecter in and revving the car up the timing seems to go up to around 28 btdc then it comes back to around 0 btdc when you rev the motor up close to where it starts to backfire at around 2800 to 3000 rpm . What the hell is going on !!!! and how do I fix it.?