Sorry shaf, i didnt read your thread properly.... but, the waxstat which reads water temp and reduces the idle accordlingy gets stuck with age and doesnt release all the way. If you stand on the passenger side of the engine bay, on the right hand side of the throttle body where your throttle cable attaches is a small screw with a sping over it. If you tighten that screw you will see it pushes the arm further away from the stop, the more you screw it in the less choke you have. Worth a try. I had a leaky gasget on mine when i first go it, idled fine was low but just a bit lumpy, you will know cos you woill get a massive waft of petrol fumes when you get on boost. It could ne a vacume line aswell.