I just recently installed the Flowmaster American Thunder Axle back onto my '11 gt. I was looking in to purchasing the BBK bolt on x pipe, which leaves the factory cats on the car. Is this a good purchase and/or is it worth the time and money? Thanks!

 

There are many good options. The restriction points in the factory exhaust are the tubular manifolds and catalytic converters (can be swapped out for longtubes and high flow cats +25-30RWHP), the section where the exhaust steps down and back up, and the factory flattened resonators. The mufflers are a TAD restrictive.

So basically, after typing that out - I guess the whole exhaust is, LOL.

Anything that you replace will net an improvement. I would do a full Magnaflow X-Pipe with high flow cats, and a nice cat-back or axle-back system.

Chris