Could be running extremely rich, so it's fouled your plugs
Also, do you have a picture of your dyno graph showing AFR's?
Take out your plugs and have a look and see if they are fouled
I was having the same problems with my previous car, because the tuner had run it too rich in certain areas, so it stalled, or wouldn't rev, or just misfired.
So I just went back and asked him to clean up the tune.