The contact owns a 2016 Ford F-150. The contact stated when the vehicle was started, the vehicle idled rough, with an abnormal chattering sound from the engine compartment. There was no warning light illuminated. The contact stated that the vehicle was losing power and was no longer able to tow the RV. The contact had taken the vehicle to a local dealer, where it was diagnosed and determined that the exhaust manifold was cracked and needed to be replaced. The vehicle was repaired. The contact stated that the failure reoccurred, and the vehicle was taken back to the same dealer who diagnosed the vehicle and determined that the replacement exhaust manifold was cracked. The vehicle was repaired. The contact stated that recently the failure reoccurred, and the vehicle was taken to an independent mechanic who diagnosed the vehicle and determined that the exhaust manifold was cracked. The vehicle was not repaired. The manufacturer was informed of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 105,000.