My 06 Colorado I5 has rough idle, poor city MPG, even after a good tune up?

My 05 I5 did the same, but I had a CEL.. I took off the throttle body and cleaned it. It did not idle rough anymore and the CEL was gone. I also had the fuel filter replaced, coolant flushed and replaced, and switched to synthetic oil; truck runs as good as new! BTW I have over 227k miles.

I'm at this point right now with my 06. Replaced many parts already, except for the lower 02 sensor. That's next. If that doesn't solve it, I'll take it in for a software upgrade. I've seen on different sites that It worked. But first I'm taking care of the codes I've gotten. Stay tuned...