[beyondloadedSE]

If i had to guess, I would say your alternator is on its way out. Adding subs will only worsen the problem, especially the louder you turn up the volume.

I would not recommend buying an svt exhaust from the dealership. $$$$ right there. Id check the contour.org classifieds. I picked mine up for $40 from a junkyard, and some people actually give them away in the southeast MI area. The only thing youll need is an exhaust hanger for the passenger side. Custom true duals will net the best gains but are the most expensive ($400-1200). Trubendz is the best bang for the buck catback exhaust.

I averaged about 30-31 mpg on the highway with my 2.5L. You may want to check your cat to see if its gone bad. That could be the reason for poor gas mileage.