Ive had 2 R5 GTTs now and if theyre looked after properly they go on and on and on...
Even if theyre modded and its done correctly then they are still reliable!
You need to use a good quality fully synth oil, change it every 6k miles, and always allow the engine to warm up & cool down properly which will also increase the life of the turbo.
Cooling is one of the main problems with this engine and if they overheat the HG goes, which is something you can avoid by sorting the cooling out. Fitting a new copper cored radiator, low temp thermostat and low temp rad fan switch will really help, plus run at least a 50:50 mix of anti-freeze in there too. I have this stuff on mine and it runs nice & cool as it should.
Mods wise, if you whack the boost up, its safe & reliable to run the standard turbo up to 15psi/1Bar (around 9-10psi standard) but for Gods sake get the fuelling sorted out or it will run lean and can f*ck the engine!
A couple of different jets for the carb and a trip to the rollers for a setup will sort this out and if theyre setup & running correctly theyll last a long time.
Combine this with a decent exhaust, an airfilter and a DV and youll have a very quick little car, probably about 150bhp and in a car only weighing 830kg (phase II GTT) then thats 180bhp/tonne and muchos rapido!
Check out
http://www.rtoc.orgwww.rtoc.org for more help & info...