Yes cold engine, disappears when warmed up. Yes next Cam belt change, get the tensioner changed and that'll cure it.
Removing the dipstick will make it run lumpy, a faulty pcv causes lumpy idling , and if by pulling out the dipstick wouldn't make any difference
![Wink :wink:](https://www.mk5golfgti.co.uk/forum/Smileys/newsmileys/wink.gif)
Your just de stabilising crankcase pressure by removing the filler cap or pulling the dipstick, which will upset the manor in which the engine stabilises it's idle.