Not seen anything conclusive on this so thought I'd see if anyone else has had something similar. The car is a 1991 Golf GTI 8v (CE2), after coming off the throttle the revs drop well below idle (around 500 rpm I'd say off the top if my head) and could be described to sound like it's going to stall, then bounce back up sometimes going a bit over 900 then settling straight back down to a normal smooth idle at 900 rpm. Mainly notice this when crawling in traffic or just after reving the engine for whatever reason. Cant say it's a massive inconvenience or concern but thought I'd post here to see if anyone else has experienced this and it can be fixed or if it's normal. For reference I've recently replaced the blue temp sensor (good quality replacement), followed RJs tuning guide (however dont have access to a CO metre so cant definitely say that's set right but it's as close as I can get by ear) and recently replaced idle control valve. Anyone know why this might be happening and how to sort it or if it's nothing really to worry about?