Clutch Problem

Seems like once I get the car running perfect, there is always something that has to go wrong. I replaced my clutch about 3000 miles ago with a King Cobra Clutch, along with a firewall adjuster, triple hook quadrant, cable, and all the other supporting stuff. Car was running good, up until about a week ago. The car usually runs fine, but every once in a while the clutch slips once I give it more than about 1/4 throttle. The weird thing is, sometimes I can get on it really hard and the clutch is fine.

Anyone ever heard of something like this? Is the clutch just faulty or is it something I have wrong with the adjustment settings? Help!