Maybe give Randy Mueller a call at Epic Motorsports and see if he has any ideas about this/about a tuning solution. The guy does race tunes for BMW's for a living. I'm sure he can get this running right/safely for you.
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1999 BMW 328i (Daily Driver) - m54b30 intake manifold, ebay headers, Rebirth Motorsports CAI, Rogue Engineering underive pulleys, Epic Motorsports Remote Dyno Tune, Custom 3 inch exhaust with Burns Merge, Schrick 264/248 Cams
1967 Buick Skylark - 430 Buick Big Block Swap.