When I rev up my engine and let off the engine almost dies for a second (really low idle) and then recovers to the set idle speed. What could cause this?

Also I gutted the the fuel shutoff solenoid and when I restart the engine after shutting it off via the shutoff lever the truck starts at a very high rpm for a second then settles to the set idle speed. This is new since the shutoff was gutted. what is that about?

I just tuned the pump and installed 3200 spring.

The vibration I had is back once I set the idle to normal. That vibration is driving me crazy. I am starting to resent this truck. If I set the idle high to get away from the vibration the rear end clunks real bad and I think its beat as the p o had the idle high. Every post says they just turned up the idle but that is not a good fix for an issue a lot of trucks had.

 

There's a possibility you didn't get the throttle linkage re-indexed properly on throttle shaft at IP. Could cause most of these symptoms.