83 xj650 Turbo Fueling issues

I have an 83 650 turbo and recently ive had an issue where after driving for a bit, the bike starts to bog down and lose power if the petcock is on, but when I switch it to off, the bike runs perfectly fine at all rpms even on boost. I’m suspecting either float seats and the needle valves, the pressure regulator, or maybe the petcock? the petcock is rebuilt but I think the wave washer is worn as that’s still original. The fuel check valve is also rebuilt, the carb is rebuilt with all the gaskets and o rings but the needles are still original. I did set the float height with the fuel pump on as well like 5 months ago. the bike is mostly all original as well, and i don’t have a fuel leaking into oil problem. any ideas on how to check what’s wrong before i buy parts?

 

Just wondering if the rubber bit with the holes in it for reserve, on, prime etc might be orientated incorrectly in the petcock?
If it can be of course.
and since you did a rebuild on it.