The reason i think the car is tuned for drag racing is his turbo choice, there is no turbo thats gonna support 500hp and spool under 4,000rpms, and with cams that sign off at 7,000rpm, that power band is to narrow for anything other then drag racing.
The second issue is the tein suspension on the sti doesnt work as well as the stock stuff, I have tested the tein flex, and the hg, both have to small shock shaft, they flex and the tire rolls over, even with 3.5 deg negative camber i could not stop the side walls from wearing, and with the stock kyb's i can! Well at least untill the shaft bushings wear out.
As for the 6spd, the ratios are to close and first is to low, 3.45 first gear is way to low for a motor supporting 400hp.
my 02 wrx with a sti 6spd with a group n gear ratio 3.0 first, pulled 1.7's 60fts, 11.20's at 120's, with a 5spd and drag gears, 2.88 first, and a cusco center diff, ran 1.48 60fts and ran 10.30's at 130's, thats what makes me say the 6spd doesnt work, turbo cars work better with wide ratio gears for drag, utilize the long torque curve and eliminating a gear change.