What RPM's is it idling at? Also, have they tried a TPS reset and a good Learn-in ride? Also, I highly recommend Iridium spark plugs (NGK# DCPR9EIX) as they're very foul-resistant and you won't have to wonder if that's the problem.
If they've not done a TPS reset, here's the procedure so you can DIY:
'08+ TPS Reset Procedure:
- Have the Run/Stop button set to Run.
- Turn the ignition key to the On position but do not crank or start the engine.
- Open the throttle fully to the stop and hold it there for one second.
- Close the throttle fully to the stop and hold it there for one second.
- Repeat the throttle open/close procedure a total of three times in succession.
- Turn the ignition key to Off/On
Follow up with a good Learn-in ride for your ECM by taking a nice long cruise 40-60mph keeping RPMs from 1500-3500.
Edit: Oh, and welcome to the Forum. :D