My 2004 dodge ram 1500 5.7 hemi has a code po303 on cylinder 3 i change the injector every thing else is good the

Hi this is Dusty, I'm one of the auto experts on RepairPal's Car Genius team. If the coil packs and spark plugs are new/good it could be a loss of compression due to a valvetrain issue, or a sealing issue with the piston rings, or a head gasket failure. I would start with swapping the ignition coil from number 3 with another cylinder, and re-testing just to confirm. In my experience (of almost 20 years), I've come across quite a few replacement parts that were bad right out of the box. Then I would do the same with the spark plug, which are especially delicate and can cause issues when damaged. If the misfire on cylinder 3 persists, then the next step would be a compression test (on all cylinders), then if that confirms the loss of compression, a leak-down test will help isolate the source of the loss of compression. If you have any questions, give us a call at (877) 913-1554