Originally Posted by beaver rs 88

Standard bosch dump valves on the 1.8t's are one of the most common faults I changed mine as soon as I got mine. It might also be worth cleaning out the throttle body and getting your mate to do a re-alignment on Vag com if he can. Heard similar faults when the coolant temp sensor has been on its way out too mate. Failing all those its gotta be an airleak. Hose under the inlet with the pressure control valve is very common for perishing and leaking causing idling issues. Hope these point you in the right direction.