While I don't remember the exact numbers I had calculated, the 1200 can have a max impeller rpm of about 40-50,000 rpm. There is a calculation to figure out that speed based upon pulley diamters and engine rpm, I'll see if I can find it. The 5500 rpm rating for 8psi is based upon a bone stock 289 which is it's effective usefull rpm. Although I have not used mine yet, I would suspect reving higher than 5500 will yield greater boost. Keep in mind more boost means more heat so an intercooler becomes necesary to keep from retarding the timing too much.