How does it run at idle? If it's running poorly then you might have a coolant temp sensor that is reading wrong.
A little more detail helps us out more since we are not there. How does it idle, does it continue to sputter or does it clean out as you rise in RPM's, does it do it engine cold or hot or both? Does it blow black smoke out the tailpipe during the the sputter? Does it run and drive just fine under cruising?
Common issues that arise can include bad MAF sensors, boost leaks, vacuum leaks, broken/old wiring and hoses, bad temp sensors, bad O2 sensors.