After 3 days of solid work I finally finish rebuilding my a15. I got it all fired up today, went for the first drive and noticed my clutch is slipping big time! Under load, the clutch just spins. A friend on mine talked about putting washes between the pressure plate and the flywheel to fix the problem? The clutch is the one of my old a12 and work fine. I

DUDE! dont put washers between the pressure plate and the flywheel! This will even further reduce the clamping force against the clutch plate, making the problem worse.
How much freeboard does the pedal have? I just bought a 310 sunny coupe who's clutch slips under heavy use. BUT< there is no freeboard in the pedal, so I belive that backing off the clutch adjustment will fix it. How far from the floor does it engage? If it's right at the top, then thats your problem. If not, then get your pressure plate tested by a clutch shop.