Running a Robinson Racing 58/17 set up with my 18cvrx. Running pavement and Road Rage II tires.

It still pulls the wheels off the ground. But, top end is much better. Keeps up with my friends Ported Sirio 12 and his is the fastest parking lot ST in our group.

I have a 18 tooth clutch bell, may be trying it out on my next day off.

Another thing you can try is to install a top end pipe, the pipe that comes with the GT is built to make torque and boy does it ever. I changed my pipe to my touring car pipe (RD Logics Turbo II) and gained a little more top end and loss just a little bottom end.