the TC is the traction control system, it's telling you that the rear tires are breaking traction. You may need better tires, or a lighter foot, which is probably the issue from your description.
As for the idle, it should be around 750 or so. 500 is a bit low. You may need some time to go thru and clean the MAF, check all the vacuume lines, and make sure the intake is clean. If that doesn't help, then I would have someone take a look at how the SRT was wired in and make sure it was done right.