Ultra XP850 Almost there!

Cruising at 45 mph with that carb [ big t/blades ], you are most likely still on the idle cct. Big-ger t/blades means you get more air with less opening, so a good chance you are operating on the idle cct.

Here is a simple test to find out without any disassembly. Find some wire about 0.025-.0.030" diam & push about 1/4" of it into the IAB. Wrap the other end around the vent tube. Do both IABs on the primaries. Secure with a tie wrap for a test drive.

If it is richer now at 45 mph cruise, you are on the idle cct. If no difference to the AFR, then it indicates you are on the main cct.