Narrative:

The aircraft's right engine was running rough and coughing at high power settings. Asked to return to [departure airport] about 3 minutes after departure. At lower power settings on approach and landing; engine was running smooth.

Google
 

Original NASA ASRS Text

Title: A Piper Navajo pilot reported a rough running engine shortly after takeoff. The pilot elected to return to the departure airport for an uneventful landing.

Narrative: The aircraft's right engine was running rough and coughing at high power settings. Asked to return to [departure airport] about 3 minutes after departure. At lower power settings on approach and landing; engine was running smooth.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.