Thanks for the response. I've changed the o-ring behind the shut-off valve as well as the one at the prefilter. I've had problem with air in the fuel lines before so I know what that feels like (more of a miss or stumble) and I'm almost 100% certain it isn't air leaks becasue this seems more like an immediate shutoff and then surge. I drove the car all over today (all under freeway speeds) and zero problems with excellent pickup and go. I also reved the engine a number of times at idle and could see no air bubbles in any of the new fuel lines. I'll check out the EGR operation .... maybe there is something with the control system. However, if the EGR works fine at lower engine speeds and lower exhaust pressure shouldn't it work even better/smoother at higher RPM's when there is more exhaust pressure and vacuum available? I'm I missing something? What control system works worse at higher RPM's? Thanks for your help.