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I think its generally recognised that with an RST Stage 1 =
Chip, exhaust, -31 and a filter to make around 170-185BHP....after this there isn't really any defined catogories!
my idea of a stage 1 is less, none chipped and boost upped to the boost limter, bout 10psi. thus making 150/160.
but this proves that really u need to pick your tuner and stick to their stages as every company does things different.
You need to look at what mods for what price to be able to compare like for like tuners