My overflow tank fills all the way up when I run over 21 lbs of boost on a 1/4 mile pass. Tried re-torque on the heads....same. Car runs cool all the time. Has new radiator cap. On a pass temp gets up to 190. Has copper head gaskets and studs. Done a pressure test on cooling system with plugs out...held 15 psi for 2 hours. Compression check showed 140 to 150 lbs per cyl. #5 plug looked like it may have a slight green tint to it. Should I just pull the heads and inspect? Have heads pressure checked once they are off?