I have a 1989 foxbody with a 5.0L and Im having electrical problems. First off mods consist of heads, cam (B303)and intake, and rockers. When i got the car it had no O2s and also no wiring harness for them either. I purchased 2 bosch O2s and a harness from latemodel. When i plugged them into the car it now surges very bad at idle 1100-1500rpm. Tried pulling the codes with 2 different scan tools, one from oriellys and the other is a snap-on, the car will not communicate with either one of them. With this being said i pulled out my wiring diagram and started checking all sensors and relays. I found that the fuel pump is directly wired to a "key hot" wire by the tailights and the inertia switch is bypassed, and i know neither should be this way. I also discovered the fuel pump relay under the hood was bad and i replaced it, it now works. However the relay under the seat will not work, even though it is good. Also while the car is at idle if you press the clutch the idle falls to around 900-1000rpm and the check engine light flashes on and off. any ideas?