CPU Spikes using Ivory 2 AU in MS 3.1.1

#Support needed: I recently installed #Synthogy's #Ivory 2 American Concert D on a MBP13 (early 2010, 8GB RAM, SSD, OSX 10). It run's absolutely fine in Ivory's standalone application. When using it with MS 3.1.1 (as AU component) I get CPU spikes when playing fast notes. Reducing sampling features e.g. string resonance etc. within Ivory doesn't help. Changing the MS audio setting (buffer size and latency) didn't solve the problem. Any hints for me would be really great. Thanks.