It's not the IS, but here's my experience with autoxing the 240SX:
My set up: N/A single cam KA, mild lowering springs, Tokico HPs (blues), no-name front+rear strut tower bars, stock sway bars, raybestos brake pads (ha ha)
Unless these guys named J.D. and T.C. show up, I can pretty much get the fastest 240sx time at the autox that day. I've beaten 240SXs with dohc KAs, SR20DETs, RB25s and full coilover suspension set ups.
This set up is pretty neutral going around Laguna Seca Raceway, but definitely need bigger brakes, because the smallish brakes faded quickly.
My suggestion? Hold off on the turbo kit and get lots of autox seat time. Remember, fully adjustable suspension set ups can bump you to a different class. Same thing with the turbo.
2004 IS300 5MT weekend cruiser
1989 240SX hatch 5MT DD, autox, track car (DSP #979)
1971, '72, '74 Celica project cars
Last edited by dsp979; 12-24-2011 at 10:29 PM.