The standard GTi's are limited to power by the K03 turbo so 250 - 260bhp ish would be the most out of that turbo. The engine however with a K04 turbo fitted like to the S3 and ED30 Golfs can comfortably run 360bhp ish reliably with stage 2 mapping with full exhaust and high pressure fuel pump.
thats just wrong.
a stage 2 car comfortably will hit 260bhp with absolutley no issue on a K03 car everytime.
and thats on JKms rollers who are renowned for their accuracy. thats just an intake and exhaust. nothinng else
add to that a stage 2+ map and fuel pump and you'll eclipse that. HPFP, intercooler, discharge pipe