2004 SAN Low RPM issue

I recently purchased a 2004 Super Air 210. I have been having issues with it cutting off if you push the throttle up around 1000RPM or if you pull the throttle back to idle from a high RPM range. It seems if I can get past the low RPM, the boat runs fantastic. I do have to put the boat in Nuetral and give it gas to get it to start. Usually pumping the gas to just about wide open throttle. But, once it is running it will idle all day long.

Here is what I have tried so far:
Full tank of gas -2 cans of sea foam
Cap, rotor and spark plugs
Replaced FCC filter

Any help would be appreciated. Thanks

I think your engine uses GM's MEFI-4 injection system.

Well we spent most of yesterday troubleshooting. I cleaned the throttle body first. No changes.

then I took it to my buddies house with a 2005 Super Air Nautique and we started swapping parts from his good running boat. (Yes I’m very lucky that my best friend let me take his perfectly running boat apart and put on my boat). We changed out the TPS sensor, no changes. We changed out the idle air sensor and no change. We put the anti siphon valve in the ultrasonic cleaner and cleaned it up. I did notice that his boat idles a little higher than mine. Is there an idle adjustment somewhere?

Also, if you go from full throttle on mine back to idle and full throttle again it will cause it to backfire two times. I’m not sure why it does this? It kind of makes me think it is getting fuel and then the spark comes back in? I’m taking guesses at this point.

open to suggestions? Thanks