with 172,000 on the clock id be wary of squeezing anything out of it over the normal
its a very open ended question, what would you like us to say? press the secret button under the dash that gives u an axtra 20 hp?
it depends what you have to spend and how daft you are, i mean u can stick a turbo unit on there but then for the cost you could get a bigger say 540 engine from a junkyard..
you dont get anything without spending big money, changing stock components gives you nothing to write home about, like air filters etc