If 12.4 is used for the maximum safe FCR, the short answer is "Yes" for 6 psi on premium gas.

The OE static C/R spec is 8.9:1... formula to find effective ratio is:

Final Compression Ratio (FCR) = (Boost / 14.7) + 1) x CR
Boost = Maximum Boost
14.7 = Psi. at Sea Level
CR = Engine Static Compression Ratio

So, [(6/14.7) + 1] x 8.9 = 12.5 FCR

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Above 6psi may be a challenge, but the ECU ignition retard helps a little. It seems fine so far on my secret blend of 10% one year old regular and 90% Exxon 93 octane premium. <img src="/forums/images/graemlins/notooth.gif" alt="" /> The main problem will probably be hearing any spark knock above the engine noise under boost.

Frank