m30 clutch puzzle

Hi guys,

Just a bit puzzled. Fitted a M30 into a E30 a few weeks ago. Yesterday the owner came with remaining parts to fit, such as clutch master cilinder and piping for oil cooler. After bleeding the clutch and double checking for air, we noticed that the clutch slipped tremendously in second gear. We than rebled the system again, only to find no air left in at all. I'm a bit puzzled on why the clutch slips on full throttle, it smells like burned clutch.In first gear the rear tires smoke with just a bit of throttle.
Never encountered this before, any of you have a suggestion on what the problem could be?

Second gear? What about first? No slipping even with the tire spin? How's the clutch action? Normal?

I might guess some sort of assembly error or parts mismatch where you have slight pressure on the clutch pressure plate fingers...