My car as noted below my signature is a 6-speed automatic V-6. The transmission has never changed smoothly enough to suit me. I've noticed at 75k miles that it doesn't seem to run as smoothly in acceleration as I believe that it used to. Seems like a bit of unsmooth gas flow almost. Does the dealer have any kind of diagnostic machine to check it out? I suppose I could just call and ask them. I suspect not. It's never been tuned but I don't think plugs are required this early. Should I try premium gas? Could there be gas filter problems? Any input is appreciated.

I tried searching this site but couldn't find anything on this.