The thing to remember with any LS1 powered Fbody is that thiis is the exact same motor that goes into the C5 Vette. GM slaps a more restrictive exhaust and airbox on them to limit the HP output to under 320. The reason for this is that it is hard to sell a guy a car for 50+ grand when there is a car available with the same power for under 30K. the Direct flow lid, and a cat back put you right where you need to be. 4:10 gears in a M6 or a 3K stall converter in an a4 put you solidly in the 12s.