4.3L v6 1997. I recently had a friend replaced the intake manifold gaskets and valve cover gaskets because of coolant leaking from intake manifold gasket. This wasn't a do it yourself job for me so i let him do it. he sealed everything and he is a straight forward guy so everything was done very well. I replaced the distributor cap and rotor. I also put in a new thermostat and flushed the coolant system. after the gaskets were replaced I heard a clacking noise coming from the engine when accelerating and it died down when i leveled out. I also got a IAC high revolutions code so I cleaned the IAC (i had recently replaced this as well) and cleaned the throttle body as well. I still have high rpm's when idling. But that doesn't worry me as much as the clacking. When i hit the throttle by hand and listen it sounds like there is a slight break right at the beginning in the clacking for about a second and then it comes back as i hold it. any help would be great

 

a video would be great, it would give us a little more insight on what it could be