One problem related to manifold/header/muffler/tail pipe has been reported for the 2010 Ford Fusion Hybrid. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2010 Ford Fusion Hybrid based on all problems reported for the 2010 Fusion Hybrid.
First time, check engine light came on when driving on highway but no apparent impact to car's functioning. Took it to the dealer. They said that the surge valve needed to be replaced at a cost of $500 "to start with", but they didn't seem very sure about it so I chose not to proceed. The check engine light had gone back off and the car was driving fine. About two weeks later on a Saturday I was driving on the highway again, at about 65 mph, when the car seemed to lose acceleration. Standing on gas pedal produced no result. Exited and was able to drive on battery power to pull over. After waiting for about 30 minutes, tried again. Check engine light was back off and car drove normally back home. Took to my regular mechanic first thing that Monday. They found oil in the intake manifold and questioned whether I had taken the car anywhere unusual for servicing, which I had not, unless you count the dealer. Did repairs at a cost of $2000. One week later, exact same thing. Car is back in shop, awaiting results.