My brother has been complaining that his truck 98. 5 24v 5spd is having a power surging problem. he first noticed it while driving down the road. well last night i got the old 84 1ton plow truck stuck and called him to give me a pull. after he got me pulled out we were standing there noone in truck and it reved right up then back down . i was like what the heck was that? he said it does it alot. any idea's?