I have an Audi 1.8t as well.
first and formost. Do an ecu chip upgrade. Its worth about 40-50 TRUE HP increase.
I got mine on Ebay, it cost me $600 with a spare ECU. It a great idea to get a spare ECU this way you dont mess with your stock one and you dont void the warrenty.
Check out Audiworld.com.
To buy a chip check out:
www.giacusa.com
and/or
www.goapr.com
ICQ me if you wanna chat. I did some other mods on mu A4