Fitted a Green replacement filter to my 900 mile Cup last night. First mod Ive done to this, or any car! Took it out for a spin afterwards, and I used the car this morning to get to work. The car feels better and you can tell its breathing easier. The throttle response seems a little better, especially at low/mid revs and the engine seems to spin up to the redline easier.
I must point out that the differences are fairly subtle, but you can feel them.
Thought Id share that with you all I think Ill wait until the cars 12 months old, so all the little niggles are ironed out, then Ill go shopping for a cat-back system