Hi Eddie, I think you're right it sounds like air in the fuel supply.Normally with the DTL + DTHs the problem is not noticed unless the car sits overnight but two weeks ago I had a customer who said it the car was parked uphill it was diff to restart after approx 1.5 hours but if parked on the flat or downhill a starting problem was barely noticable even overnight. The only thing I could think of was gravity was helping the fuel back towards the tank due to the usual air leak at the leak off pipes. Check to see if the leak off pipes feed back into the fuel inlet to the pump(great design) and if they do get the vac pump out. Hth Sean