I have been using a efilive tune in my truck for about 2 years now and never had a problem. since it got cold 5th gear has limited 2 times under medium acceleration at 55 MPH. the way the tune works is i have no boost until around 55% throttle then it jumps and i start to get good power. The power output is not much over stock just the way i get power is little different.

Do you think my trans is toasted or something else might be going on?

codes i have are
P0700
P0735

Them Codes suggest that your tranny is slipping 5th gear... which usually points to worn Clutches...

Check your oil level and try changing the spin on filter...

The tune could be making it shift when boost and power comes in and the tranny might not be able to take it. Not saying yours is but bad tunning can ruin a built tranny let alone a stock one.

my friend changed it this past week. i put stock back in there and will leave it. the awesome fuel economy will have to be on the way side i guess

Your Operating system might not suport it, I know it did not on my 05. But you can set the fuel quantity vs speed to limit fueling at a certain speed when it shifts to 5th gear.

I am trading it in so it is back to stock now. Let some one else deal with it