<<<I'd think you'd need around 100-104 Octane for 21psi in a static condition using a modified 20G or 16G.>>>
Yeah, to make that power on either of those turbos you WOULD need race gas. However, in your in-depth knowledge of how cars work, you didn't take into account turbocharger efficiency. Before you make ANY assumptions of how much boost a car can run at a certain C/R, you would have to look at a compressor map of the turbocharger on that car. An efficient turbo that doesn't heat up intake temps can run higher boost on normal gas than a smaller or inefficient turbo that just blows a lot of hot air. Temperature is the key here.
<<<Also what was the ignition timing at 6500rpm? Was it at 20deg or around 12deg? I ask because I know that the boost level a person can run depends on the timing that they run at WOT. So it'd be neat if you can run over 12deg timing on 94Oct and 21psi with a 9:1 compression ratio.>>>
Again, this question is about as meaningless at the question "so how much boost are you running?" It's all dependant on other factors. You would need to know what is going on inside his motor. With a DSM, you are talking about a car with a very efficient cylinder head design, and a dished piston. If he did his homework and polished the combustion chambers, they should be very free of hot spots which are prone to detonation. With enough fuel, and proper tuning, you can run as much timing as you want so long as you don't cross the threshold of detonation. My point is, you picked two numbers out of the clear blue sky, and 2 very different numbers I might add, both of which would have little or no signifigance on this particular car. For instance, I ran 20 pounds of boost on nitrous with 33 degrees of total timing at 7K rpm on 120 octane leaded race gas and made 423HP, 428TQ to the wheels on a small unclipped 16g. Does that make sense in any equation? No, you would obviously need to know more. I'm not trying to come off harsh, but the questions you asked were all too specific in their vagueness...