intermittent surging while driving

[rp performance]

I am having this issue with my 99 7.3 that is intermittent so even harder to pin point. I have seen some other treads here on this but did not see any that where intermittent. My truck is a manual trans with a Diablo tuner. I thought that the tuner might have been an issue so put the stock tune in with no fix. One day it runs fine with no issue and the next day it acts up. Basically it will sometimes start to accelerate with no change the accelerator. Sometimes it feels flat when you change gears. I still have not had the CC recall done on the truck but do not think that could be it. Any ideas would be great as I will be using this towing a lot this summer.