Hey deanp
here is a link to what another user has done to his sc400 and hes gotten ALOT of power out of these cars
http://us.lexusownersclub.com/forums/index...22&hl=jibby
this is probably one of the best descriptions on modifications that ive seen on this site. it has helped me a bunch. the 400's are pretty restricted stock, upgrading the exhaust(rod millen, magnaflow,megan), ECU(Apexi,UNICHIP,Jet) , torque converter (if you are going to keep your 400 auto,this is a MUST for quick speeds of the line), intake, those and some other upgrades will give you a good start on how much power these engines really have. hope this helps