What Drives are you using? - try SSD if possible
Are you dropping frames? How many movies are you playing back at a time?
Re-code the photoJPEGs to AI should help.
Check the image quality - in most cases 50% will do not 100%
What is your final output? Projector?
What resolution are you running with TH2G - If going to a scan converter, can you reduce the output resolution in to the scan converter?

m171 is a custom version I think - so Richard may be able to suggest more...

Simon