Sounds like the same problem I had on a vectra, do you notice any difference wethers it's facing uphill or down hill, if the problem only occurs when facing uphill it's most likely the fuel is running back to the tank if the fuel filter is situated high on the bulk head, fuel pump has to work extra hard to get the fuel up, atb
Just bought myself a fladen jacket, for out mooching about, not had the chance to try it yet, will update if it's any good, £50 out of go outdoors,atb whatever you get,Defo no good for ferreting in the brambles,lol