Hey and welcome to torquecars mate.
1st up is make sure its been serviced properly, if not get that done first. oil changes have been done on time with decent oil, timing belts been done along with water pump etc
then start on the performance.
1st up would be a remap ( may have to be chipped on the '98car. if its got a diagnosic port it can be remaped ) this should see you around the 180-190 mark for around £300-500 depending on where you go and if its a generic map (like VAG have put on it, all the same) or a custom map.