I have DMH low profile cutouts that were made for the GTO. I have not been able to test them at the track, but it's on my list to do. Currently they are blocked off and need to bee sent back because they were leaking.(3 year warranty). I really hated the sound of them, open V6 just sounds horrible. I could feel a definite loss on low end torque and top end seemed to be stronger. Sadly our track has been closed for a while now and might never open, so who knows when I will get some real 1/4 mile data. Rob says they are good for some power on his car and 1-2mph in the 1/4.