Gotta be .63 when i changed mine from .48 i ragged it home from buying my .63 let it cool down, 3 hours later ragged it down the road with the .63 on and i was as happy as a dog with 2 dicks, didnt really notice the extra lag but like turboshed said you cant beat that kick up the arse. Also anywhere near 400bhp and the .43 is way too restrictive