Tune to make shifts less firm?

I have a shift kit in the car right now that came with it when i bought it. It is set so that when the car shifts i loose traction real bad between 1st and 2nd. I don't know much about transmissions so i am looking for a fix without opening it up. I was wondering if a mail order tune could help with my problem and make the shift less aggressive? I have seen that you can make the shift firmer so maybe it can go the other way also. The more horsepower i keep adding to my car, the worse the problem gets.

In normal driving the transmission shifts relatively softly. If your shift kit makes this too hard, I don't think any reprogramming is going to help. You would need to remove or modify the shift kit.

I called a transmission shop and he said they probably drilled holes and put in stiffer springs so they would have to be replaced with new parts. He was guessing $400-$500 total. What do you think of his estimate and solution?

Unless you know exactly what was done to it, you won't know what it will take to put it back to normal.

Commanding less line pressure should soften the shifts, in theory. It depends what the shift kit did to the trans though.