I did exactly what you're asking.
Had E90M3 and moved to X5M about 7 months ago.
If you have any specific questions, I will try to answer or if you wanna talk, we can talk over the phone too. PM me.
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PAST: F80 M3 ZCP | 911.1 C2S | F10 M5 ZCP | E70 X5M | E90 M3 | E46 M3 | E36 M3
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