A tuner will not hard the engine or transmission. Just use the preinstalled tunes with the appropriate octane of fuel. I run 93 octane and the 93 octane tune with no issues. Tows better too.

 

I have heard of your first problem before. It turned out to be a problem with the computer and the MDS was not turning off when it was kicked down. It was just running on 4 cylinders. You may want to check the wires and plugs on your tranny. There may be a loose connection preventing the kick down from working properly...

 

Thanks for the responses guys. Really appreciate it.

The tuner is something I'm thinking about.

I'll check those wires and make sure everything is tightened up. When you heard of this problem before, did the person who experienced the problem have any warning lights on the dash go off?