RE: STALLING
This is a duplicate of my friend's .46 FX problem.
The solution was found when he determined the hole in the exhaust nipple, in the muffler, did not go completely through. No presure to the tank, and in fact it would create a vacuum in the tank after running a while, and fuel would no longer flow.
You might check to see if the hole goes all the way through your exhaust nipple. (I'm assuming you used the same muffler on those 3 engines.)
Good luck,
Dave Olson