I just put on MAC headers, and now it seems like i can stall out alot easier than before, and when driving on the freeway at about 1700rpm in 6th, if i floor it, the shifter bounces around and the transmission seems like its struggling....but it would never do this before. is this from a drop in low end torque from putting the headers on?

Second, when im stopped and i have my foot on the brake pedal, i can feel a slight pop against the pedal. I dont know if its from an exaust leak or what...but feels like something is causing a slight popping under the pedal...

im just wondering what could cause this, or if its normal

 

First of all, the transmission/engine are struggling. You're not supposed to floor it in 6th gear, you need to downshift first. As far as your shifter bouncing around, either your exhaust isn't tightened down or you've broken a tranny mount and/or torque arm bushing. I'm not sure what could be popping against your brake pedal, I never had any problems with my Macs.

 

does it only "pop" around till about 2k rpm? and the car doesnt accelerate much?? id put money your wires got screwed during the install or theyre touching one of the primaries and are burnt could also be a cracked plug but id lean more towards the wires had the same problem as yourself after my install as well, thats what it wound up beeing hth