how much will a si final gear me down at highway speeds. I understand si=quicker acceleration, but at what costs. 4th gear in my old rx7 feels like 5th in stock zc, so if i like to go fast . don't mess with it. i got a eurospect tranns for my scirocco with a taller 5th and that was great, so i guess i should leave it alone. none of them are ever perfect i guess. everybody says zc with si final is the quickest, but you cant keep up with BMW's on the throughway . basically i have both tannys is it really worth the work to make the hybrid