Hi, Haldex oil & filter should be first on your list. Audi will tell you there is no filter to replace but there is.
A VAG indy will normally do the job correctly.
if you have receipts for the other 2, the fuel filter will be O.K for many years, but replacing the air & pollen filter is recommended.
Hoggy.

 

There's actually two filters on the Gen2 and Gen4; a cartridge for the Haldex and a litte plastic filter screen that goes on the end of the pump. Both of these are overlooked since Audi removed them from the Service Schedule.

More here on various service issue for the Mk2 -

FAQ - Audi TT (8J) Recommended Maintenance & Service

Thanks to Barr_End for this excellent list of maintenance topics. :) The standard Audi maintenance schedule does not cover many of these issues, and from over a decade of Mk2 experience, these recommendations should be followed, especially by new owners who may not have a service history for...

www.ttforum.co.uk

Specifics on the Haldex -

FAQ - Haldex Service & Filter Replacement

This topic has been around a long time and comes up again and again. How often should the Haldex Clutch get an oil change and should the filters get changed too? According to the Audi Maintenance Schedule for 2006, the Haldex oil and filters should be changed at 35/75k miles or 55/115k...

www.ttforum.co.uk