OP, you are as good as you're going to get for the time being.
It would be news to me if an N55 powered car has dyno'd over 400whp yet (that includes Dynojets).
N55 Turbo upgrade hope:
http://www.e90post.com/forums/showthread.php?t=848459
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2024 BMW M3 Sedan Frozen Pure Grey II/Fjord Blue, 6MT
Past: 2021 Z4 M40i Frozen Grey II/Black Alcantara | 2017 F30 340i Mineral Gray/Coral Red, 6MT | 2011 E92 335i Le Mans Blue/Black, 6MT