i have guessed my e.t.'s to be around a 13 flat.. and i can just squeeze by the new LS1's. i raced a 2001 6-speed ss once.. he had loud pipes and who knows what else... but the ol' GN still took him on 225/60 radial t/a's. i've got fairly basic add-ons. like stainless exhaust, big IC, k&n, 3"downpipe,headers, and my 200-r has some trick work done... im only runnin 15psi. and i can bark overdrive at 115mph and slightly larger 255/60's.. but i gotta say.. those LS1's have some awesome technology behind em. i'd love to play around with one of those.