hey my truck is throwing a p0380 code... which means a bad glow plug or controller. how is the best way i can test for this? when i fire it up and its cold (like 50* or colder) i have one of my cylinders that has quite a bit higher injector balance rate, but once it warms up, its just like all the others. Is that a sign that possibly my cylinder #1 glow plug is the bad one? or what is the best way to test to see which one(s) need replaced?