I have a 2009 LT Cobalt with 2.2L engine that was overheated. The mechanic replaced it with a 2.4L engine. He said he used the 2.2 manifolds on the replacement engine. It ran unevenly until I unplugged the varible valve sensors. That appeared to take care of most of the problem except it is now hard to start. Is there a way to make this 2.4 engine work properly in this car; such as changing the head or the electronic engine controls? The dealership said this engine would not work.