some of the polo 1.2s are fitted with chains. they do stretch and ocassionaly jump teeth. the stretched chain gives cam position faults.
probably done half a dozen chain kits in the last year. never had to put valves in one tho. had one thats intake cam had jumped by 4 teeth! how nothing contacted is a miracle.
I'm an AA Patrol and am starting to see this fault on the road side. Vehicle will often sound like its flooded and wanting to start. Usualy you can here the chain rattaling a bit on crank. I was informed by a VW tech that there is a guide that breaks up causing the chain to go slack. Is this what you are seeing as well davieboy?