I have a 97 12 valve 1 ton manual transmission dually. when under a med to heavy load the throttle starts to hop a little which makes the truck jump. if i rest my foot next to the transmission housing it seems to help. my mechanic says all my throttle springs are ok and not broken. on bumpy roads (potholes) it is alot worse i have to either take my foot off the pedal or mash on it. im worried whats going to happen if this keeps up. does anyone know about this or suggestions to fix it. Thanks