ok, so heres an interesting spin,

i got the old surge tank back and when i look at it the fittings to and from the tank are larger (maybe 12mm), but the to and from engine fittings are still only 5/16 ish, just the same as the moke tank..

so im thinking that wont fix the problem..

You should have the outlet pipe from tank goes to lift pump to surge tank, the pressure pump (in tank is best) goes to engine via filter, then fuel return goes back to surge tank, not main tank.

yes this is correct, but im saying the outlet from the surge tank, that goes to the high pressure pump is the same as the outlet on the moke tank,

so in theory it will choke as much as the moke tank is suspected to be,

i will check the flow tomorrow and make sure its pumping the ammount it should be (LPM)

Just a silly thought, you don't have a filter between the tank and the pump do you?

No, the filter is between the pump and the engine

That eliminates that then!

Sounds like the surge tank needs reworking or scrapping, If it's restricted on inlet of HP pump it won't work.

ok, so i have solved the problem!

turns out the fuel regulator on the engine wasnt Daihatsu, it was installed by the previous owner who did the conversion,

needless to say it wasnt letting any fuel through, so the fuel pump was constantly pushing against it,

soon as i put a new one in there, no more hot fuel pump !

Good work.