Do you still have the previous VM image available?I did a fresh new installation, furthermore documenting each steps, and some of the problems I had before didn't show up...
I don't have a specific guess at what to look at but if you have the previous VM with the performance issues and the new/fresh one that doesn't show them there might be a good chance of being able to narrow it down - especially if you can make both images available to the community for testing/inspection.