2013 8600 air issue

My 2013 Transtar 8600 with MF 11 air compressor cycles way to much. Compressor loads after 4-5 miles on the highway with no brake application. At idle, with or without brakes set, both tanks only drop 15 psi in 30 mins. Only loses air when revved up. Both tanks drop to 50 psi overnight. New compressor, (not rebuilt) and governor were installed 6 months ago but it was losing air before then. New rear chambers last week; no improvement. Have used gallons of soapy water and found just a couple small leaks. Took it to the dealer this week and they only found small leaks that didn’t improve the cycling at all. Waste of time and money. Thanks for any suggestions