The stock K14 turbo on the om606 is spooled up and making peak torque at 1500 rpm. You can't get much quicker than that. I saw recently on ebay a K16 upgrade to the K14 turbo. An upgrade compressor housing and billet compressor wheel, keeping the hotside stock. I think this would produce/move more volume but still keeping the same spool time.

https://www.ebay.com/itm/NEW-K16-Turbo-Compressor-Cover-with-Compressor-wheel-Back-plate-K14-Upgrade-/302201575238