They are rated at 305/320 from the flywheel. If someone is putting down more than the flywheel rating to the rear wheels with an h-pipe and a filter then that is a serious gain. Assuming 15% driveline loss you are looking at 358/376! If you really want to get serious you could do the aviator intake which is the poor man's FR500. It has long runners for the low range and then short runners for the upper RPMs. There is plenty to do: headers and full exhaust, air intake, intake manifold work, 99/01 cams, tune, aluminum flywheel/driveshaft, gears, and suspension. I just read over at Corral that there are filter/mid-pipe cars running mid 12s.