shaking on acceleration

Hi can anyone help

I have a 2005 1.9 tdi with DSG box the car has done nearly 90k miles.

in April I put new tyres on had the gearbox oil changed and paid an eye watering amount for a new Dual Mass Flywheel.

Since the DMF was done a fault hardly noticeable at first has got slowly worse and my local garage could not find anything wrong.

When accelerating between 40 and 55 the car shakes side to side but the steering is unaffected.The shaking is proportional to how hard I accelerate, as I tow a touring caravan on holiday going uphill on a motorway can be very worrying. I also get some juddering if pulling away from lights too fast whilst towing (not wheel spin).

Cruising with the caravan at 60 the car is smooth and steady.

Before I go back to my local garage has anyone got any ideas?