KIA Sedona 2002. Stuttering, running rough, hesitation.

About a week ago I started the KIA (rainy and in the 40s) and it was
running rough under acceleration. It never stalled though. I filled it
up and put some STP fuel injector cleaner in it. Upon leaving the pumps
it was running better in a matter of minutes. And no I don't believe it
was the STP. I took it in for an oil change and during their PM they
didn't see anything irregular. How well they check I don't know. You
would think these days they would throw ever car that came in on the
diagnostic machine for free and make money on the parts and labor they
would sell.
Anyways, today, about 5 days later and at a 1/4 a tank it starts acting
up again. Same weather. I am going to go fill it up and see if that
fixes it. The only thing that might tell me (This is my theory) is that
the fuel pump might be weak or filter clogged and needs more
Gravity/pressure to work. I'll run some more STP thru it.

It has about 65,00 miles on it. So I think I'll start with Plugs and
wires. Is NGK the recommended ones here in the group. Is there a good
online parts store to order from?

Thanks,
Phil