Tiguan 2009 epc check engine and oil lights come on

I’ve recently had the cam chain replaced and
2 pistons (due to damage from the chain)
also I’ve had the oil and filters changed. Now
my 2.0 tsi  petrol engine sounds like a diesel.
The check engine light epc light and oils light
turns on and off. I do notice that it turns on
when I’m in traffic (low revvs) not sure if it’s
connected or not. I’ve taken it to VW but they
say no problem. I know something is wrong
but not sure what. Anyone else have this
issue at all