I have also driven a mess of Z's. I had a stage 10 whatever Z and when i first got my supra the Z was just spanking it. I put 6k into the supra[single/fmic/etc..] and went to have it tuned and made 500rwhp. I have a friend who had a 700rwhp supra and nothing was done internal all was bolt on. Also it was done by him and a friend. I still love the Z for the all around performance and am in the process of building another, but just wished there was a way to blend the two.