Could be a lightweight flywheel There no Throw out bearing in this car its a Retaining bearing and Slave cylinder combo, Ford only charges 400 for labor for the SVT that how much they charged me. Did you check the Master Clutch Cylinder? Because mine made this chatter and I thought it be a Retaining bearing Slave Cylinder but it was the Clutch Master Cylinder leaking, depends on miles but your Clutch Fork can be worn also.
166WHP/147TQ Running Rich at flat 12! More power to come once finished!