Rough Idle on my 2010

I bought my 2010 Tacoma Quad Cab V6 2WD Auto in June. This past weekend I took it to the dealer for my 5000 mile check-up. When I pulled out I noticed some hesitation then at the gas station on the corner it was idling rough. I took it back and explained what was up. They looked under the hood, checking vacuum hoses, etc. All looked good but idle was rough. Tech said he only changed oil and checked air filter, fluid levels, etc. I drove it around town but after 2 hours it was starting to bug me so I took it back. They couldn't find anything obviously wrong so they rebooted the computer. They said it should even out after a few weeks of driving. But a week later it is still rough. I have filled it up twice since and I can see that my MPG's went from 20-21 avg. to 18 MPG's. Any suggestions? Next week if nothing improves it is going back to the dealer.