Well, most GT3 owners alread know what to do. But in case you don't:

get a car that downforce settings can be changed

-set both spring rates to lowest

-set both ride heights to lowest

-set both of each limited slip (intial torque, acceleration, and deceleration) to lowest

-set final gear ratio to 3.000

-set auto setting gear ratio to widest

-set front downforce to lowest, rear downforce to HIGHEST

If you have a gameshark, then use the nitro "NOS" code for even for speed.

 

oops, i forgot to type this in- set front downforce to lowest, rear downforce to HIGHEST.

I also got 520 MPH with Calsonic Skyline.

NOTE: I tried some non-rear spoiler cars that could have downforce settings changed, but it still didn't lift.

 

if your car has VDC, then set it to lowest

 

I also got 390 with Denso Supra and

290 with C5R Corvette. Look at all those SPARKS FLYING EVERYWHERE!!