Yep. I struggled for two laps thinking how bad I got after missing a day of driving until I jumped out and checked the settings and saw I was on the harder tires.
I had a low mileage Fairlady Z Z-tune (Z33) '03 pop up in the used dealer. From the UCD it's rated 508 with dirty oil. Lowered the down force in the rear to 5 and then adjusted the chip (turned the engine down until it reached 500PP) and took it for a spin. I must admit I've never been a fan of the milddle age Fairlady/Z's (this one being newer of course), but this thing is a blast. Nice revs, excellent grip, a bit of a gurgle instead of the usual high pitch wine and against what I would have thought, it almost begs to be thrown around versus the usual steady in and steady out.
It'll beat the Shelby by 10-15 seconds depending on the course. The car can easily be dropped in PP and raced for more money. Plus for a standard the inside is nice enough to drive from the cab view.