I have owned a 2001 Challenger for 1 year and have never had a problem with it until yesterday. Both engines run fine until I try to increase the speed. RPMs are maxing out at 3600 rpm in both engines. Engine RPMs flutter beyond 3600. I checked both fuel separators for water and contamination, all are ok. I inspected and replaced spark plugs, still no help. I removed the air intake boxes and poured a small amount of gas in both carbs to see if RPMs would increase to eliminate fuel restriction problem. This did not help. What would cause the RPMs to be limited like this? I would appreciate any suggestions.