Is your car your daily driver? If so, I've found it difficult to cut weight w/ conv's and maintain the comfort level. I agree w/ fiveoboy that chassis tuning is worth it, but disagree on the tire pressure. My recommendation would be to run the highest pressure you can w/o spinning. This allows the smallest surface area of tire to be touching (dragging, slowing you down) the ground. Also, a set of skinnies w/ 50 psi was worth as much as 3 tenths over my ponies and 245/50's for my car (on radials).
As far as I know, most tracks will not let you race w/ the top down (it really doesn't make much difference in traction anyway), but I asked just for kicks and they said they'd let me run if I had a 10-pt. Guess that won't be happening!!
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93 yellow limited edition convertible
Black top/interior, 5-spd
3.73's, H-pipe, pullies
Best - 14.13 @ 96.5 on street tires
3650 lbs w/ me.
My desperate attempt to get some pics up -
http://cperryman.tripod.com/grid1.html