a body shop should be able to help you with the vents. means cutting into the wings/bonnet and respraying.
performance wise you want to stay subtle
have a look at a remap. revo seem to get a lot of rave reviews should see around the 200bhp-220 mark and 225ftlb.
http://www.revotechnik.com/products/softwareProduct.aspx?pvID=785 thats for the 150bhp engine. theres about 7 variations of this engine. most of the ones between 150 and 200 bhp are more of less the same engine with different forms of the map.
changing the standard recirectuating valve for a performance one will help along with lasting longer than the standard ones, prone to bursting seals.
ive smoothed my airbox in the bora and it seems to have increased airflow, its feels sharper when putting the foot down. im looking at putting a panel filter in as well.
if your really want some power a swap to a k04 turbo will allow you up to 300bhp ( k03 should be maxed at 210 and k03s 240) this swap should might be easier with the A4 as is its engine not mounted longitudinally rather than transverse like most of the other setups.
keep the oil changes reqular even if you use the longlife as the 1.8t is prone to sluding, at a cost of around £3-4k to fix
also a good idea to get it checked for engine faults and error codes