goindownhole

On my 87 GT, I just installed a full mac exhaust system.

Now, it will idle but does not want to run if you give it throttle and tries to die.
Car has a new fuel regulator and a new fuel filter as well.

The only mod to the car is longtubes, prochamber, and catback. It ran fine before the header install. Fuel pump kicks in like it should, seems to have good pressure although a gauge has not been put on the schraeder yet.

What else could it be?

Boss_Hotrod

You did install the o2 sensors back right? seems stupid but a lot of people over look that. Also if you put an adjustable regulator on it then you need a gauge to check the pressure. Might be too low.