Farmerpete. I am not sure that your engine behaves the same as the 1HT engine, but if it does:
Remove the facet pump from the fuel delivery line. It cannot pass enough fuel for that engine. It pumps a lot more fuel than the engine needs and the restriction may cause the symptoms you have.
If you need a primer pump put it in the return line to suck the fuel thru the filter and IP. This could cause issues with the IP internal pressures though.
If running on veggie oil increase the fuel delivery line to 1/2"ID to further minimise restriction.
Check posts by Tim HJ61
Hope this helps,