Thanks for coming back guys, I have the original downpipes (headers) but the end section is an ART carbon end can, and pipe, down to the underbelly original section.
I was hoping many overtime have removed their seized EXUP valve, for either YZF750R or similar engine in other YAMAHA. I don't want to experiment with various jets, and float heights and keep putting back together to test, only to find again not running right.
I am really looking for a done before this way or that, and have a final solution. It has been a long hard slog getting to this stage (a year) and while it is fun above 3,500 RPM. I would love it to be a little more user friendly.