I'm not 100% sure. I only ever check cylinder pressure against what the manual says, so you might be right. If it is 12.5:1 then I should be able to run higher octane fuel than the 91 octane everyone says you should run in these engines? Not sure it will give me anymore power without me changing the timing. I'm not at that stage yet, but I do know the ZXR cams are 'fixed' as is the timing wheel, so not sure how to try and get anymore power out of this thing.