Mk4 Golf GTI 1.8t misfire

[2 GKC]

We have had this car in the family since it was a year old. Took it to a garage for a timing belt and after it came back it was misfiring. It went back to the garage and they couldn’t find a problem, said timing was spot on.
Been to two other garages since who agreed the timing is ok. One then did all four coil packs, which made no difference.

The misfire seems to be worse from warm starts and is generally at low revs. Car still has plenty of power when not misfiring.

At a bit of a loss what to do. The last (VW specialist) garage said he would have to start taking the engine apart at great cost because he had checked all the obvious stuff.

It’s too good to scrap (80k miles)

Any one had this and or got any recommendations please?

[Belle427]

So if it were fine pre belt change my suspicious mind is telling me something they have done has caused it whatever that may be.
Does the car log any fault codes?