Well I would say of course do the fluid and filter. You should have the tcm scanned and ecm scanned for fault codes. I would say this might not even be tranny related, It could be your cat convertor is plugged up. It could be the plug wires, its hard to say. When was the last time those 2 were changed along with the fuel filter.

So I would suggest you change the fluid and filter, do a complete tune-up. If that doesn't work I would look at the cat. It could still be other issues but those are guesses.