I have a 1990 nissan 240sx with a KA24de engine swap that someone put dc headers on it. It also has the EGR tube cut and pinched off and no O2 sensor. It seems to run fine once it gets going down the road, But when it is cold it does start and goes to about 2500 rpm and idles for a sec. Then it will drop and start to stall out either way if I press the brake pedal it will try to stall out, I have to keep the rpm up or it will just drop. Also when I press the brake pedal the interior light (if on - sitting with the door open) will dim when I press the brakes. After it gets warm it will run a little bit better and idle correctly but if I hit the brakes it will try to stall again. Also if I try to turn the lights on it will drop my idle about 200 rpm same with if I turn the heat or AC on full fan speed.

I am not sure what is causing this, I have looked for vacuum leaks, Checked the IACV.

I did try to unplug the MAF sensor and if it is not going anywhere it will idle perfect with it unplugged but will not take off if i try to drive it. Absolutely no power if i unplug it. So I have plugged it back in but it is still really rough.

Also when I try to take off it will be very jerky taking off unless my rpm is over 1500 rpm. otherwise the entire car jerks back and fourth and feels like i am miss firing but then takes off after 1500 rpm and runs fine.

Any ideas?

Simply put, running a modern ECM controlled car is pretty much impossible by removing the most important sensor it needs to operate correctly............the O2. It pretty much regulates the engine at idle once it has gone to closed loop. Without it the ECM has to revert to limp mode failure fuel maps that in no way will have the car running 100% right.