4L60E shifting issues
Mail-order tunes are often oriented towards higher stall converters which make shifts softer.
I don't understand what you mean by "really hangs in each gear before shifting".
If the tuning software is in the distant future, you should take the truck to a local (not chain) trans shop and have them connect their scanner and pressure guage to determine what is going on. If you do that, post their results and comments here before committing to any major expense; we will try to give you guidance.





