RE: TC31 OS .21 VZ-M
i heard what you are speaking of in the 1st video (but not the 2nd video BTW). Just a comment.... I'm gradually working on shortening up my pipe (different boat & engine) and it was mentioned to me that when I got too short on the pipe, one of the possible symptoms I might see would be the engine sagging in the corners.... which leads me to toss out that you might want to try lengthening your pipe a little as the possible culprit.