200 HPDI still Stalling

[blissful1]

Still having troble with my HPDI. Will start and run, but below 1300 rpm will cut out. If you reprime bulb, it will start right up and run. Runs great from 1300 rpm to 5000rpm, but as you get close to top end, 5400 rpm, will cut out. Once again, if you reprime, will start right up. Have changed in line filters 2 times and drained fuel cup and vst.

Local mechanic doesn't think it is a fuel/ethenol problem; says to change O-ring on fuel cup (might have pinhole since the cup has been removed and installed numerous times recently), then check anti-siphone valve, primer bulb and fuel line. We both belive there must be a small airleak, as the bulb is soft after cutting out.

Any thoughts from anyone out there? Thanks again for your responses.

[99yam40]

monitor both fuel high pressure and medium pressure as problem occurs to see what is going on. There are multiple filter/screens in that system along with screens in the injectors that will plug up. You can even monitor the suction pressure to see if there is a restriction. The proper test equipment is why the shops get the big bucks.
If you run a motor lean on fuel because of plugged filters it will eat pistons.

[blissful1]

Any idea of the time required to perform this diagnostic test? Is it done in the shop or out on the water? Should I bother to look for an air leak or stuck anti-siphon valve first, or just suck it up for the diagnostic test? Thanks!