I think normal road use the are fine.
I have one on my Edition at 2+ @ 360 ish,I did notice some loss of power on track as the day went on at an open pit lane but thats giving it welly reaching 140/150 on one straight also I won best in my class @ Inters on the Sunday doing the quarter mile so not too shabby,it was a very hot day and you are sitting waiting in the queue for half an hour before getting your turn.