I dont reckon the aussie 1.8s had 100 hp. I think they had 90.

All things are achieveable, but not on a budget.

For budget performance you will be better off getting a bigger capacity later engine and bolting it in.

By the time you take your 8v apart and rebuild it you will have spent thousands.

Worth bearing in mind that a 16v will need different ecu and fuelling etc which will add to the cost.

Cheapest mods you could do to make your car faster would be change the head for an 8v Kjet head from the UK or South Africa, they have a bigger cam as stock, whilst you are there put a Mk3 downpipe and manifold on it for better flow.

When all that is done get a UK digifant ecu which chucks more fuel in and you will be at or over the 110hp of the UK GTIs and have a more torquey and revvy motor.