tbh mate it will be a waste of money ! u just hav to look on here to see the amount of dissapointed people with 172/182s who have attempted to tune them. needs about £2000 spent for 18bhp.
I have a 200bhp car that has cost me alot more then that. As Andyman says you should get a fairly cheap/proven package now that others have gone through the pain.
I would definately get some H&R or Leda (I think they are back in business?) coilovers properly setup it will cost around 1k for the H&Rs but will transform the car.
It is only a waste of money if your expectations are to high, you are thinking of selling the car within the next couple of years or you do not own the correct car (ie. really want a RWD or 4x4 turbo).
I spoke to a chap recently who is into 200sx. He told me you can tune a turbo easily but when you shove an extra 100bhp through transmission and diffs etc something else will go pop then you have to uprate it. Just increasing boost or bolting on bigger turbos makes for a car that is nothing...nothing... BANG, it certainly is big power but big fun? More scary then fun IMO especially on slippery winter road on your way back from work.
I bought my clio brand new three years ago and have got cams coilovers etc. etc. I still find it exciting to drive especially when still within legal speed limits. I hope to still own it in 10 years time so I can gloat at the people who have just bought the latest lardy dumbed down 1400kg 250bhp clio. They arent getting any better are they?
Speak to BenR at AWT IMO if you go ahead. He knows his s**t.