My 5k problem, is the ironhorse suppose to shut down or is it suppose to studer, I find very few people that talk about there ironhorse.
Iron Horse or Big Dog they both have S&S motors same as Swift, Titan and all the others.
I think you should fix your accelerator problem or re-build the carb then re-assess you carb issue. I can't help you with an issue at 5K as I never get that high!
But you might refresh everyones memory here and tell us what size motor you have and what jets are in the carb. You location will help also. Include intake and exhaust.
But if you are asking about Hi rev limitsm, BDM are set at about 6250 I believe and your AIH should be similar at around the 6000 RPM mark.