The usuals for us include:
Headers (Tri-y for low-mid range gain, 4-1 for top end)
Twin 2 1/2" Cat-back system.
For the M6, 3.91 or some guys are using 4.11 with either a full spool or mini-spool centre (for the drags, but also on the street (not quite legal here, though)). For the A4, 3.73 or 3.91 with a T/C.
Our tuners seem to have a pretty good grasp on LS1Edit and are regularly seeing gains of over 50rwhp over stock.
Larger MAF to Throttle Body pipe (4" ought to do it)
Enlarging the hole in the front of the airbox or replacement with a pod-type filter.
Then Cam, then heads, then stroke it, then blow it, then..........
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