The car seems to idle the same. The first start up was a little "gassy" smelling and rough for a few seconds, but I am guessing that was just the extra fuel in those 3 cylinders.

It is hard to tell if there is anything "louder" in the front with the FWI being so loud. I am not sure how to test for the vacuum leaks or exhaust leaks.

Could I be running "lean" and just hit some threshold with the PLOG (not one individual piece was causing it, but the PLOG, FWI, and Downpipe together did???)???