Exhaust modifications are one thing.
There are in theory two cats in the Aero exhaust - one at the top before the pipes split left and right and on each side in the wings.
you could in theory improve the airflow by takign the cats out first. Even improving the headers will not make a great deal of difference without some work here too I would think.
Cerial - we need you as you actually know a but about this kind of thing!
Harry I'm assuming you mean the main manifolds coming off the engine?
