Hi I have a 2005 mustang gt that starts to get a knocking sound and he car rattles after driving about 20 miles. it runs fine on start up but after I run it for a while and come to a stop it will start knocking on the left side of the engine and it feels like it wants to turn off. The noise goes away if I rev the engine. The check engine light comes on and reads code p0340 which is camshaft position sensor I changed both and the alternator. What can be the problem please help.