Have you done testing to see how broad the boost range is then? i.e. boost comes in at 2000rpm and 'lasts' until 6000rpm based on exhaust backpressure that you deem acceptable? Are you desiring pretty low rpm boost for when you autocross? Still lots of work to do on my car but I settled on a VSRacing 76/75 with a T4 1.25 a/r to try to find one responsive but not choking.