I'm a new member and have a question for all you experts.

I have a 2001 Xterra with the 3.3V6 Auto. I had the timing belt, water pump, thermostat and head gaskets changed recently.
When the car is in drive, and idling, the idle is low (650RPM) and a little rough. It has 127K miles on it. I have replaced the plugs, leads and fluids. Could it have a fuel injection issue? And if so what is the best course of action? The MPG has also dropped in the last month by about 2mpg.

Thanks for any advice.

Bob