Too much boost?

I checked the coolant in my 97 gtp and i noticed that it was extremely filthy. I don't know yet if it is oil or just dirt mixed in there. I sure hope its not oil because this would mean that i probably blew a head gasket. The car only has 74000 miles on it!! I bought the car a few months ago, so I don't know if the previous owner ever flushed it. The thing that worries me now is if it got too much boost. I put a 3.4 inch pulley on it, and my boost guage shows about 12psi. Do any of you think that this could have caused a gasket to blow? I would think that if it is a gasket, the car would give me some sort of a sign. However, it runs great, the oil looks good, and the water temperature is always normal. I was hoping that maybe someone could help me out here.
Thanks!

With only 74K miles I doubt the smaller pulley is the cause. It sounds like you need the old coolant probably Dexcool flushed out and just need new coolant. A lot of us have switched over to the Prestone Extended Life (yellow container). Dexcool looks terrible after several years. A lot of us have modded at that mileage with no problems noted.

Just double check for any possible cross contamination in the engine oil and cooling system. If you get a bad supercharger, lower intake manifold or head gasket you would have driveability issues including overheating, etc.

Thanks a bunch. I will flush it probably tomorow, and then i'll find out if it stays clean or not after a few miles of driving.

Thanks again for the info!