My car is in the process of gettting a 5psi T-25 turbo on it, and I'm wondering if I should change plugs to a different heat range? I have the NGK BKR6E-11 plugs in my car right now. I know iSR has the 7 and 8 heat range NGK's, but is a hotter (assuming a higher number for NGK means hotter) plug what I want, or is colder better? I was thinking of BKR5E-11, but I'm not sure. Thanks!