Since the swap I've had this annoying vibration. Today I decided to trouble-shoot it and it turned out to be the damn spring/bolt combo connecting the header flange to the cat. Seems the springs were getting pushed around when the joint flexed and knocking against the damned lip on the cat's flange. Tried some bigger washers and torqued the bolts down tighter but that didn't fix it for longer than a few minutes. Decided to just turn on the lathe and make some custom aluminum washers with a recessed seat that would hold the springs in place. A half hour later, no more annoying vibration. God....I don't know how I ever survived without this damned thing.

 

swap?