Chrysler Repair: error code 300 on chrysler 300., crank sensor, leak fuel

Question
my engine was rumbling when I reach 100 to 110 km.  check codes and got a 300 and 302.  misfire with plug #2 and the other was general.  went to dealership, they change the plugs, 6 of them and still getting the rumbling with error code 300 only.  They don't know what can be causing this issue.  should they go ahead and change the coil packs on the car.  can  you tell me where I can find them.

Answer
Hi Steve,
I think more diagnosis needs to be done before any other parts are changed out. There are test instruments available at a good shop to do that. It could be one of a number of possibilities:
intake manifold leak, fuel injector/other fuel system problem, spark coil(s), erratic cam or crank sensor signal, mechanical problem with engine proper. So I would try to find a sharp tune up mechanic who can quickly identify why this is happening which will be the most efficient way to solve it.  You didn't specify the year, but likely the coil "pack"  is found at each spark plug...one for each plug, not a cheap fix to change all of them as far as part costs go.
Roland