Check the float level. Sounds like the carb is running low on fuel supply at those prolonged RPMs. Also the petcock can be abbreviating the fuel supply at high RPMs.I bought a 1998 dyna wide glide when I really getting in it it falls on its face about 90 mph or when I really getting one it in 4th or 5th I don’t think it’s a carb issue because I bought a new one and already mess with the jets a couple time but still does the same thing it runs good when I moobing on the back roads but as soon as I get on the high way it bogs down and falls on its face about 85-90 mph but then I can let out for a sec get back in it and it’ll be fine for a sec then do it again anyone ever seen this problem just looking for help
Albeit your bike only has a stock top calibrated speed of 110mph. The stock ignition has an integrated rev limiter. If your bike has other than stock those specs change with the setup.
You didn't tell us what other mods your bike has yet. High flows, stage 1, 2 or 3 ? That info always helps the techs to figure shit out !