You said "it will run all day under 4000 rpm, but if I run over it stalls after 2-4 minutes depending on load & rpms (@5000 2 minutes, @ 4300 4 minutes)" ..... but once you restart, it runs fine at all rpm's - is that correct?
If so, then that is pretty darn strange. It sounds like fuel starvation at the higher rpms, that clears itself after re-start. Your timing above (2 minutes, 4 minutes) corresponds roughly to the amount of fuel resident in the VST.
Now, let's back up - what's in front of the VST in terms of fuel flow? The low pressure fuel pump, and the low pressure fuel filter, the low pressure filter bowl, and the fuel/water seperator bowl. Are tou using a Racor-type external fuel/water seperator filter external to the engine? If so, when was the last time it was changed? They do get clogged up. Starting from there, go to the onboard fuel/water seperator and make sure the bowl is properly seated and there is no fuel leakage. Next go to the low pressure filter and bowl. You said you changed the filter, but how good are the connecting fuel lines? Is the bowl seated properly? Any leaks? Check the leads to the LP fuel pump and make sure they are tight and there is no corrosion on the contacts.
If all that checks out, let me know. The next step is to test/pull the lp fuel pump.