A couple of weeks ago while towing in appalling weather the engine hesitated a number of times when under high loads and full(ish) throttle. Had it been a petrol engine, I would have said it was a misfire. Assuming the problem to be fuel related I changed the fuel filter. I am convinced the filter had never been changed (car is Aug 0 despite having been serviced by dealers each year by the previous owner (fuel filter should be changed every 2 years). I have towed since under the same circumstances and no more problems. I am also convinced that it is driving more smoothly!

For interest, I followed the instructions in the Steve Rush Service Manual purchased off eBay. It is brilliant, very clear instruction and easy to follow. Well worth the money.