it would be good to put a temp gauge in that thing, but, the direct clutch may be slipping, which has nothing to do with your converter. is it an automatic valve body? is your throttle pressure linkage adjusted properly? it could be a line pressure issue, inadequate clutch disc clearance, or possibly a clutch piston seal problem, among others. fwiw, i have a "high horsepower high stall" car that gets driven on the street- a lot!