The N55 build path
Stage 1 is software only. No downpipe, no intake, no parts to source or fit. A custom remap moves boost and timing well past the factory settings, and the mid-range gain is noticeable from the first drive. Stage 2 adds a downpipe and intake: the engine breathes properly and you land in the 390–420 bhp range. E85 is the biggest step on the stock turbo. A flex-fuel kit and ethanol map push the ceiling to 420+ bhp, with more timing and boost than pump fuel will allow. From there, an upgraded turbo opens the door to larger bespoke builds. The N55 is an older platform now, so Samuel calibrates from your datalogs and to your fuel rather than running a generic file on a used engine.