I'm in the same boat. I've been debating whether to remove second cat and resonator or do OEM exhaust mod. Did you not get the sound increase you were looking for with CAT removal? I'm also having issues finding a shop to do the OEM exhaust mod.
2007 E90 335i Sedan - Montego Blue Metallic with Black Dakota Leather, Brushed Aluminum Trim, 6 Speed, Sport/Premium/Cold Weather Packages, Comfort Access, Aluminum Pedals, Window Tint
Mods:Active Autowerke Processor, BMS DCI