I had a 21x9x3 core and it was night and day at the track but it still wasn't enough on its own, you'll also need a much larger oil cooler and maybe even something different for the radiator. It just depends on how long you want to support 500hp. After 30 minutes on the track I found that the intercooler would get hot on the intake side but the oil temps would sky rocket as well as the egt's. I think for 500+ HP you will also need a tubular header, port and polished head, port matched intake and exhaust, different valvetrain, and probably more but like I say, it just depends on how long you want to run it at full throttle. I always used 100+ octane and would cut my run session short by 5 minuts to avoid the oil temps from getting to high. Good luck.

Elijah

Vast stage 3+ fueling, K04/RS6 turboed work truck/track whore/DD
<br/>By elijahallen, shot with u40D,S500,uD500 at 2008-07-19