imranian hi,Gtti got 993cc,DOHC,turbocharged,intercooled,12valve,Efi,3cylinder engine.Gtti got very strong engine internals which can easily take upto 16-18psi of turbo boost without upgrading anything.Stock PSI,turbo boost of gtti turbo is 8psi.
Gtti is still the world fastest 1000cc car as it beated renault R5 turbo which used to be the fastest hatchback car of the world.Many Car magzines inculding Road & Track and Car & driver (1988-89) called Gtti's engine bullet proof engine.As far as i know Gtti interior and exterior designs were designed by an Italian company and it used to be called Pint Ferrari in Europe back in late 80's and early 90's.Gtti engine is capable of producing about 150BHP without upgrading internals,turbo,ecu.Stock Gtti is 100BHP,the one i own is GTxx which is roughly 115BHP..The only difference between Gtti anf GTxx is that gtxx got turbo cooled turbo,rear red lights and extended front and rear bumpers,engine and power is same.
Stock 0-100km time of a stock gtti is 7.8seconds..and with little mods it can go 0-100km in about 7.2-7.5 seconds.I have seen few gtti's in UK producing 175BHP and running 0-100km in late 6seconds(e.g 6.5+-).
If you dont drive it like you stole it i will give you mileage of 10-12KM/Ltr and if you want to drive it hard and fast then i might give you a very low mileage and that is about 7-8KM/ltr.
Spares are very cheap in pakistan for gtti/gtxx as u can use normal 1000cc charade headgas kit in gtti engine,shocks,clutch plate,pressure plate, and almost all the spares are avalible in market,new and second hand both.
thats all i know about my fav. hatchback,and please correct me if i am wrong mates.