...I'm scared to death about the engine failures and possibly popping turbos (thanks forums). I would also like some feedback on modifying to a reliable level.
Much is going to depend on how the car is driven.
If you keep your foot out of it, you won't be operating at high boost levels very often. The anecdotal evidence suggests that engine can sustain high-boost (above stock) excursions for infrequent, short periods of time likely to be experienced on the street or drag strip, premature turbo popping notwithstanding. However, I think it is safe to assume that the engine experiences increased wear and tear when operated outside of its design envelope. How much wear and tear is anybody's guess.
OTOH, tracking (e.g., HPDE) a car is a very different scenario. In this case, I'd be very concerned about the effect of a tune on reliability of sustained (20-30 minute) intervals at or near WOT. I think it is easy to imagine both mechanical and thermal stresses exceeding what the engine can sustain and still be considered reliable for many years. There doesn't seem to be much anecdotal evidence. Correct me if I'm wrong, but I think that the Golf TCR power is equivalent to the Golf R, and while the TCR engines seem to be fairly reliable, they aren't bulletproof, and I'm guessing must be rebuilt somewhat frequently.
