03 95 changed plugs now there's a hitch in her getalong, plugs or transmission?

[3aeros]

2003 95 aero wagon that we bought back in April. Currently has 107,000 miles on it, just changed plugs bought the ones that the owners manual recommends, the original factory plugs were still in it when we changed them. Since the change when you stomp on it or put it in sport mode and get on it there is some stumbling. Don't know the history on transmission service and can't tell if it is that the plugs are not the ones you guys recommend or if it is the dreaded transmission troubles that plague these vehicles. Thinking about putting the old plugs back in just to see what happens. No codes thrown by the way. And the gas mileage on the first tank went up by like 4ish MPG. Haven't flushed the trans yet but do plan to do that asap. Thanks for any ideas.

[Mike Brennan]

It seems, although I have no proof, that new plugs seem to kill off marginal DICs. I suggest you get a code reader from Auto Zone or advanced Auto. They let you use them free. I suspect you will get a 1334 code. You will need a new DIC.
Be sere to get an OEM unit from them or Rock Auto sells OEM as well. By the way, the 02 5 speed did have some issues, but not in your year. It is a good gearbox. Be sure to change it the 3 times method if you dont know when last changed.
Also, if you dont know if you have had the Mod #6 done, finds out and do it. You should also drop the pan to check for sludge.