Can you please add some more details to your description?
- Did the software vendor give specific instructions for virtualizing the application?
- Is the database remote or local?
- Does the issue still happen when the VM is running alone on the host?
- Do you see any kind of bottle neck within the guest OS?
- What hardware specs does the host have?
- What hardware specs does the physical server have?
- What exactly is horribly slow, how can you measure this?
- Did you pull a performance log bundle from the host or had a look at esxtop yet? (http://www.yellow-bricks.com/esxtop/)