HELP! Some brake troubles here...

[Mecom Racer]

Some background: I'm using a booster/master cylinder and calipers from a '96 Corvette. My engine is a 2002 LS6. Most of the time the brakes work great but I don't have long periods of driving logged onto it yet...

Here's the problem: It doesn't happen all the time which really confuses me. I thought we had this problem licked but it seems to have come back.... when the car and brakes cool back down, the problem goes away.

Sometimes while driving, I'll notice some resistance between shifts which gradually increases into the brakes being applied at all times - like driving with the brakes applied. It seems the calipers aren't releasing and it gradually end up clamping tighter and tighter. When it happens, the brake pedal is stiff and way up at the top. What the hell is going on???