Hello Carl and welcome to iRV2.com and to the Gulf Stream Owners Forum. We are glad to have you join us here and we look forward to reading of your adventures and experiences. I am sure you will enjoy the website and forums.
Congratulations on your Sun Voyager. I would suspect the problem could be fuel pump and heat. I had a Aerbus that would do the same thing if I did not stay at highway speed. It was a weak fuel pump down in the tank. Are you by chance on a Ford chassis?
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7