Been having a few problems over the last few weeks with the S3. It seems to be after lengthy motorway journeys only, if i turn the car car off and go back to it say 15/30/60/120 mins later it'll fire up and the revs will drop so far that it cuts out. Once i restart it, it'll usually fire up ok the 2nd time but the idle is like a pile of ****, up and down unless i give it a bit of throttle and it seems ok. It also has started takin a bit longer for the engine to fire up once ive turned the key although this doesnt happem all of the time. Short journeys, it seems ok for some reason. Any help would be greatly appreciated.