Coolant pressure AUDI A6 Avant (4G5, 4GD, C7)

HI. I’ve had the car for just shy of 3 years. It’s a 3.0tdi v6. I think I’ve inherited lots of problems. When accelerating hard or towing, the coolant is pressurised causing ut to expel from the pressure relief valve. Main dealer us useless,  apart from taking money!. They only checked at unless, which is fine. I keep coming tk the same conclusion, that the head gasket us on its way out. I have replaced the coolant valve along with all the gaskets in the ‘vee’ and also had a new egr cooler from tps. The problem is still there. I would like some advise, as pulling the engine out us a huge job and don’t want to pull it out unnecessarily. All avice welcome

Regards Scott