Exhaust vs power-steering

Are you using the Center Force Pressure Plate with all the weights on it? I have used that in two hemi swaps and both times the cars have had bad vibrations. I had the the flywheel and pressure plate checked and the pressure plate was out 50 g and the flywheel was out .5 g .The machine shop said that they couldnt balance it and that is why they stop selling them. Changed the pressure plate to a HAYS non weighted one and all is good.
I have used them behind big and small blocks in the past with no problems. I asked the machine shop that and he thought that the hemi's rotating assembly is much lighter then the old motors and made it more sensitive to the out of balance.