Kawasaki Pro FX models.

Only thing I can think of that you haven't already done is look at the fuel pump. There is a filter on it but you have to pull the pump to look at it. If that is the problem consider installing an inline filter before the pump.

Greetings All, I'm looking for the most effective way to quiet the noise inside the cab. The cab virtually sits atop the 24hp diesel engine. It's very loud and so I'm looking for ways to make inside the cab quieter.  

Well, it appears all it needed was some time.  After several attempts, it started to idle just fine.  After reassuring myself that it appeared to be running well, I took it out on the road for some "run" time.  It was sluggish to get rolling (like the belt wasn't gripping) but after a few miles it got much better.   I think it had been sitting for quite a while and things just needed to break in a little.  After several miles both the engine and drive train seems to function normally (at least what I would expect). The only thing that concerns me at this point is the high-end engine RPM.  Does anyone know what kind of max- RPM's I could/should expect from the engine?  Right now it seems to start bogging down in the over 4k range (sometimes it will get to 4200).  Not sure where the ECM starts clipping the RPM's at.  The ECM I purchased at Motorcycle Doctor was the "enhanced tune" unit that is supposed to allow for another 500-RPM's.  Is 4k all I can expect from the engine ?  Additionally, occasionally, the engine hesitates a little from a complete stop, but quickly picks up and takes off.  That may work itself out with some more miles on it.  But all in all... things are looking promising at this point.  It appears the ECM (the WRONG ECM) was the main issue from the beginning.  I suspect when the original owner bought the new ECM, and that didn't work to get the engine running again... he threw his hands up and quit.  Little did he know that either he ordered the wrong ECM, or, the company simply pulled and shipped the wrong one. 

Quick test.  Sounds like the fuel pump is not keeping up with demand.  After the 30 sec or so run time, and starts to die,  give it a wiff of starter fluid and see if it recovers........fuel starved. Key OFF wait 5 sec or so....Key  ON only------no start position.  The fuel pump is turned on for about 5 sec to PRIME/PRESSURIZE fuel rail.....signal is from the ECM.......wait it out for time out......then start.     Listen for the short prime time running.  Start.....ECM should now keep the fuel pump full time. Put a test light on the pump connector (clamp to Gnd) and check for 12v.  Then reverse the clamp connector from Ground to a hot +12v.....you can now check for a good ground at the connector.

UPDATE:  Got the new ECU today.   Installed it and the engine fired right up !  Success... but it will only idle for about 30-45 seconds, then dies like someone cut the power.  Cycle the key and it fires right back up, and I'm talking immediately.   Runs another 30-45 seconds, then dies again.  Plenty of fuel pressure, will test again tomorrow to get actual numbers.  Right now I'm thinking Idle Air Control.  I'll remove that tomorrow and check it out.  I have no idea how long the machine has been sitting without running.  Good news is though, the engine sounds strong when it is running.  I'll report back on any progress.