This is strange and disappointing since I just purchased the LPE clutch for mine. I haven't had it on the road yet as I am at the tail end of a supercharged 416 stroker build.
Not sure whether it makes that much of a difference, but those who have added a separate clutch fluid reservoir find that it has solved the problem IDK. There are a number of theories on why this happens, some say it is fluid temperature, some blamed it on the stock pressure plate but I don't think anyone has actually found the real cause. If it is none of these, that only leaves the master clutch cylinder. The last I heard, there is no replacement or upgrade for the master cylinder.
__________________
666 EVIL RWHP BUILT AND TUNED BY SHIFTED PERCEPTIONS INC.(SPi)
416 Forged Stroker, E-Force Supercharger, Blower Cam, Rotofab CAI, Stainless Works 2" LT Headers and 3" Exhaust, LPE ZR1 Twin Disc Clutch, DSS 1400 HP Axles, Pfadt Performance Kit Stage 3.