Truck started running rough and would not idle without the choke so I checked things out and applied vacuum to the top of the EGR valve and as normal, it almost stalled. When I removed vacuum, it seemed as if something was dislodged (dirt or carbon build up) because then it ran OK again. Is this a sign the EGR valve is dirty inside? I see NAPA sells them for $220, but CoolCruisers sells them (Special Order) for $189. Or is there a way to clean it out. Thanks. 1987 fj60; 2f.