Terry,
I used to hold the track record about a million years ago at Portland in an ITS 240Z. We used to run 3.9 gears and a limited slip. Portland turn 1 (especially) and other turns tend to be long and sweeping. A locked rear end will cause a lot of scrub. I don't know the current state of set up for those cars, but we'd run a stiff setup since the track was pretty smooth and flat.

Check with Jon Wilson and Joe Harlan out there. They will know all the hot setup parameters for that track.

Steve Spiers