I have 2 foreman 400s one 1997 and one 1999 and both of them are experiencing misses and bogging when you are really pushing it to climb a hill or swimming in the mud and snow. I have talked to a few dealers with little to no results. I ride anywhere from 5,000-10,000 feet in elevation. Any help would be greatly appreciated!! No mods have been done to either machine just the routine maint.