2.5 tdi water pump 20 tooth pully

[tebar]

Hi Everyone,
Im new to the forum and need some advice regarding my water pump,
Firstly,the engine in my van is the same as whats in an a6 from around 1996,its the 5 cylinder tdi unit,When i went to change the water pump the original had 18 teeth on it(its run of cambelt),
I got a qh replacement part and it states in the box that vw changed the pully to a 20 tooth item,and if the new pump is being fitted to a petrol engine the camshaft pully must also be changed........... it stresses that this only applies to petrol engines,
I was going to just put it in and try it but not sure if the belt will fit?? also could it affect my timing????

Help on this matter would be much appreciated,,,,,,,,

Thank you.