I have a 2000 blazer with a 4.3L. I keep getting the PO507 code.What is happening is when you let off the gas to stop the RPMs stay about 1100 till you come to a stop, for about 3 seconds then it drops to about 600. I replaced the spider injectors about 6 months ago as it was bad. It seems since then its some what been acting up.Ive replaced the IAC valve also. The trouble codes suggest possible vaccum leak.Any help would be great

 

Mine is kinda doing the same thing.

Does your's feel like it is bucking or running out of gas when coming to a stop but still trying to go? On mine, when coming to a stop, it sometimes "bucks" "surges" whatever you call it, causing me to put extra pressure on the brake pedal then it idles down. Sometimes it does it sometimes it's somewhat fine.

All this happened when I cleaned the throttle body with it still on the car. Also at 35mph it would accelerate on it's own.

Not trying to hijack your thread, just trying to compare symptoms.

 

Yes some what but no bucking