Missing at 3000rpms

I have been chasing a similar problem. I started a thread on the electricle forum, but I think I have eliminated all possible elec./ignition problems. Is there a way to test seat pressure with the heads installed on the car? Would a compression test reveal anything? I have three cylinders showing 150 psi, all the rest are at about 175. I rolled each cylinder up to tdc and put about 30 psi of air into them. None seemed to leak out the intake or exhaust, but they all sounded like air was leaking past the rings into the crankcase.