2000 Quad 4 Hesitation/Stumbling

Car started stumbling noticably at idle over a week ago. More recently started doing the same at speed during steady throttle. Seems ok under acceleration, might be a bit down on power, hard to tell.

Figured it wouldn't hurt to change the plugs either way so we did that on the weekend and dumped in a can of injector cleaner.

Seems to be slowly getting a little bit worse. No trouble codes thown yet but I imagine it won't be much longer.

Car is a 2000, 4cyl quad with 90,000km on it. Automatic transmition.

Next on the list of wild ass guesses it to chnage the fuel filter. Other than that I don't really want to do much guessing.

Any suggestions?

check for a vacum leak around the intake first off, then it probley wouldnt hurt to change the fuel filter as they are inexpensive and usually overlooked.
But dirty injectors, and those coil pack are a couple other things that can go bad.

Might not hurt after the injector cleaners gone thru is to treat it after you replace the fuel filter. Another inexpensive remedy.
Oh and Welcome to AF!