Might be a dumb question, but what if any effect on mixture will less or more flow have on a. Weber equipped engine

A rule of thumb is that less exhaust back pressure requires some jetting enrichment. How much of a jetting change depends on what change you're making to your exhaust (e.g. just swapping mufflers vs. going to an open exhaust for a track day). A typical jetting adjustment would be one of two main jet sizes.

My muffler is really old. I think my jets are close, might be time to try a new muffler. A buddy followed me and said I smell like i am running Rich