If it is the boot door seals/rubbers then as stated previously, Krytox works wonders. I used it on my front door seals and it completely eliminated the noise problem I was having (was recommended to me by Beddie and GS Wax). Did the rest of the car with it just for good measure. Not cheap for a small bottle but worth it.
Available from TPS, part no. G052172A1 VW Krytox (DuPont GPL-105). 30ml £28 plus VAT