HM headers and Lukey exhaust?

[ADM]

The best exhaust mod you can do is to fit HM headers and a VRX rear muffler. It's not loud and you'll gain genuine power. Any after market muffler is questionable and in my experience loses power and creates more noise.

Agreed about the HM's, but any decent aftermarket muffler that is a straight through design 2.5" in - offset /out - centre will free up more power compared to the stock baffled muffler.
I have a stainless magnaflow straight through on my AWD for example, same design & virtually identical size to stock baffled muffler.