The Mk4 2.0 8V is 115 BHP in standard form, As the mk4 golf is a heavy car this is not really enough to give most what thay expect from a GTI.
A Citroen Saxo VTS for example has 120 bhp in a small much lighter car!!
Your not going to get gains like you can from a 1.8T or GTTDI unless you spend lots of money on a turbo or supercharger kit, Even then reliably could be an issue.
However you can to the following to help get it running at its best.
1. You can remap the car although gains are not massive Could be worth doing at the right price and it will sharpen throttle response. Speak to nick from R-Tech. (
www.r-techpower.co.uk/)
2. Performance exhaust,Air filter/ airbox mod and DSG intake will help.
3. Make sure the car is serviced properly.
The 2.0 8V engines tend to use a bit of oil this is normal.
If you do short journeys you can get condensation and "moyo" on the filler cap - Bare this in mind before you think the head gasket has gone.