car running bad....

I had my car in a local shop here getting some work done. They installed my QTP heades, QTP y-pipe, MSD wires, NGK plugs, and borla cat-back. The 1st day I got it back it ran like crap and my ses light starting flashing at me. I stopped by Thunder Racing and one of my spark plug wires was loose. They will be giving it a basic tune this Monday. My problem is that I don't have the low-end tourqe like I use to have before. When I take off it just lags a bit then it takes off eventually. I here a little knocking underneath my car, wtf? Has anybody had this happen to them before? What fixed the problem? Will the tune take care of this. I'm just really sick that I had all this work done and my car runs like crap and it seems slower.:cuss:

It may "seem" slower on the low end but the top end will more than make up for it. Let Thunder tune it. If the y pipe is banging the floor board, tell them. They should be able to take care of that as well. I bet a "post long tube" quarter mile ET slip will say your car is faster.

Don't go back to that local shop, if they gave you the car back with loose wires then they're not worth a shit...especially after spending the money that you did there.

What would a cracked spark plug cause the car to do? It just hesitates before it takes off. Seems like it is missing. I've noticed my gas mileage seems shitty!

Is the ses light still flashing? A crack plug can cause a miss..

Its not flashing anymore. It just stays on. He told me the tune will turn it off. I guess my questions is, is this normal after a header install for it to seems like it lagging on the low end. It doesn't want to spin the tires like it use to.

Never heard anything but good about Thunder. When they tune it the SES light will go off.

Long tube headers will make your gas milaege take a dump. Maybe you should have looked into the pros and cons before doing these mods.

I did my research but I didn't think it would be this bad. Hopefully the tune will fix alot of my problems.

Make sure your sensors (MAF, front O2's, etc.) are connected and working properly. If they couldn't hook up a plug wire right, who knows what else they may have missed.