« Reply #9 on: 25 July 2013, 00:07 »
there are differences between the two but not enough to warrent the cost of upgrading over a K03s based on experience having both turbos.
K04-001 seem to max out around 260-270 and K03s 240-250 without WMI, both make around the same amounts torque wise, given the cost of a geniune K04-001 it is a lot of money for 10-20bhp more something that a meth setup could do for a lot less on a K03s.
If changing turbo again I would much rather go for a good proven reliable hybrid than a K04-001

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2003 1.8T GTI 180 - APR Stage I, S2000 Filter, R-Tech Supersize TIP, Bilstein B12 Suspension, 18" OZ Superleggera, Recaro Heated Leathers, US Spec Rear Lights, N249/SAI/PCV Delete
1.8T AUQ - 241bhp & 286 ft-lb
R-Tech Map, Forge FMIC, SFS Oversized TIP, Ported Manifold, Milltek Turboback non res exhaust, Forge 007p, N249 & N112 delete, SAI delete, S2000 Air Filter, Sachs clutch & Lightweight Flywheel