all mk3's are chain, be it petrol/diesel 4 pot or V6.
no need for changes unless somat starts to go wrong with it & the only maintenance that is sugested is a inspection & adjustment ( if required ) every 100k miles or so ( got told by my local dealer to leave it alone unless i suspect somat is wrong as they have inspected a few mk3 taxi's on high miles and had to do nothing apart from hand over the bill for around £150 ish for the job )