All of the street legal kits are in the 6-8 psi range for our cars. But if you rev to 9K on a stock civic you'll tear it up just as fast as with a bad turbo and too much boost. And don't forget that you HAVE to use premium. There's also the equation of the differing condensation points of petroleum and it's ability to burn given the ambient temperature. the 6-8 psi range is good if you occasionally get a bad tank of gas. at 9 psi you are gambling if you have no internal mods and marginal compression.