Ok, and a few more facts after that! OS--F plug a MUST! The 5 just doesn't cut the mustard, runs too cold. Midrange goes to pieces.

I normally run mine 1-1/5 to 1-3/4 turns out, but the manual settings are just a starting point to get the thing to go. Change out the plug, put in an F, stretch the pipe out an inch, start it up at 1-1/2 turns, and then try leaning it out from there. I have found that the OS pipe, here at 3000 ft alt, still needs to be stretched out a bit to run the big props. Works at stock length ok with a 16-13 or a 16-14, but I found that with a 14 pitch prop, couldn't get the plane to slow down enought for me.
The 17 inchers give you good braking and the 13 pitch gives really consistent speeds. But, you have to stretch out the pipe to get it to work! The midrange just will not work at shorter pipe lengths with the big props.

I have also tried backing out the pump, with some success, but leave that alone for now. Voids the warranty and all that.

Short of any of that working, poss pump problem? But wouldn't think so at this point.

Keep us posted.