Hi MarcusG!
Since you are able to get the max frame rate in MAX, your connections are working well. The issue, therefore, is with the software. In other words, your processor is doing other things in the background and preventing you from acquiring at the max frame rate.
Try using a sequence instead- there is an example in the NI Example Finder called Sequence.vi. (Appropriate name, huh? J). The sequence should allow you to acquire at the max frame rate.
Kristen H.