Diesel exhaust fumes ingress when stationary

I can't find my original thread on this, so will repeat myself and see what can be suggested.

Skoda Superb Mk2, 2014 4x4 Tour de France now @ 92K miles.

Engine as per factory, 2 litre and runs a dream, starts well no matter what and totally serviced to schedule from new.

Almost from new but noticeably so after 3 years in we would have exhaust fumes enter the cabin when stationary and when the stop/start function was not engaged (ie towing).

Local AUDI independent specialist tried to find the problem and concluded it was the gasket from he turbo to the Cat, really a metal shim and a big clamp.

This was changed but issue still there.

Seems to be worse now, so seaking advice please on the problem and the fix.

From the previous thread of about 3 years ago I think someone said it was a 'thing/valve' by the turbo that will have cracked, leaking fumes and this is right by the fresh air intake, hence the ingress.

Part is cheap, labour could be £800 as it is a 4/4 and the gearbox size is right in the way, turbo off etc.

On cold start I can feel no blowing, hear no blowing and the area around the turbo is not sooty. After about 60k miles there must be some evidence to find?

So, any thoughts please?