What highways runs? From what speeds? What mods on your 600?
Hauling ass down highways, trying to pass traffic to make my exit ramp. From 65 or 70 to 130 with no problem, and plenty of juice left. Only mod (performance wise) is a two brothers exhaust system. And all I ever do it kick it down to 5th from 6th. If I really wanted to haul ass, I could kick it down to 2nd or 3rd.