@KTL,

You got the right burst rate. I can burn 16X with both 162I and 3500AG with no problems, but I have the 1394 builtin on my motherboard on my laptop.

Some things to check:
1. HD Defragged ?
2. Are you trying to burn from a compressed directory ?
3. Other activity on the PCI Bus ?
4. Have you checked CPU usage ?