I have a 2013 ram 1500 2 wheel drive. with the 5.7 hemi. I think it has VVT. It idles fine. But when under a load it has a bad miss, until it levels out then again runs fine. It is sending a code that #4 cyl. is misfiring. I have changed the coil, plugs, and injector. Is this a prob. with the...