One of the signs on a 6spd. C4 is the clutch grabs very high, this is a sure sign it's worn. On a 4+3 the clutch pedal gets realy hard to press down. Yes you can go and try to make it slip but sometimes that will only happen when it's shot, down shift and pop the clutch is also a good way to shock the clutch and see if it's slips. I have come across a few cars in the past that did not slip at the time but when the clutch was removed I don't know just why it wasn's slipping it was that bad, I'm sure just a little bit longer or one good lanch and they mak have been walking.
How have you been? If your clutch pedel is engaging high up off the floor, not down low near the floor, then you are probably in the last 10% of clutch life. If that's the case, you should start thinking about a replacement clutch. What kind of hp and torque are you putting out? Maybe someone else could inform us on how much hp a stock LT 4 clutch can easily hold. Is there any difference between a LT-1 and LT-4 clutch? Would an LSx series clutch assembly fit a C4? Or is the next step a Centerforce or another aftermarket assembly? My inquiring mind would like to know..