[Z-linkCobra]

Have you pulled the pan on the motor? I dont how they balanced the crank but if they added weight could one of the weights have come off? At this point I think you have gone past the point of the clutch and all that. I think pull the pan and give a good visual inspection. Make sure there aint nothing floating around in the pan thats supposed to be attached to the crank.

just for S%*ts and giggles...do a compression test on all 8 cyls if its not too much trouble just to make sure.

Just some thoughts.