Mine does it also, but I think mine has to do with the cams. Mine was from the day one. Both of my Stallions had the same clutch chatter with the cams. If I raise the rpm to around 850, no chatter. One of the cars was with the stock clutch, the current has the McCleod RST Twin Disk
2007 Foose Stallion "The Prowler"
FRPP Polished Whipple SC - 8lb boost, FRPP Hot Rod Cams (M-6550-3V), FRPP Ceramic Coated Shorty Headers, FRPP Tuned Racing Suspension, MagnaFlow Magnapack Catback, Steeda TriAx, Nexus Series - AFM, Vac/Boost, Fuel Pressure, Speed of Sound Dash Pod, Raptor Blue LED Shift Light. 425 RWHP 387 TQ