I have an '89 F350 w/7.3L IDI. Currently it has been surging (rpm increasing) when stopped at stoplights and sometime it will do this while driving down the road. Usually after it has been driven a while. 180K miles on the truck now and I bought it at an auction with 140K so I am unsure of the history before I got it. I am thinking it is possibly a problem with the injector pump? I probably need to replace the injectors and fuel filter soon as well (definitly wont hurt).