Loss of power on Motorway

[mike74]

I have 1.9 petrol Dg caravelle and have been having a few problems with the van losing power on the motorway, it runs fine around town but soon as I hit the motorway it suffers loss of power and backfires with the speed dropping to about 40mph. I recently had the rubber fuel neck changed and the tank removed and cleaned as I kept getting blocked filters but it has got worse since this was done. I have changed the filter on several occasions before the tank was cleaned and after. Another problem I had which might be related was after about a two hour journey the van wouldnt start and I had to leave it a couple of of hours and then it did, I guess because the engine had cooled. I am thinking that maybe some crud has got into the carb? Fuel pump?