Code P303, And also P300
 

Hello, I am new to the forum, I have active code PO303 and PO300, I have changed all plugs and wires, new coil, cleaned out the throttle body, also replaced the intake orings and R&R THE PCV. The engine was running rough before the CEL came on for a while. I originally had a intake leak at the #1 intake, which I diagnosed with spraying brake cleaner around the intake manifold, I heard the engine idle change and could visually see the cleaner get sucked in, so like I said I replaced all of the intake orings then I get this CEL for the #3 misfire, and random misfire. I have taken the manifold back out and rechecked my work, I didn't clean the ports at first, so I did it this time but it still has that code and sounds like a helicopter at idle, I have not done a compression check yet because the engine is not knocking, nor is it burning oil, I do however have small amount of oil in the throttle body hose. Any suggestions? Thanks for your time.

Have you swapped injectors to see if the misfire moves?

It can knock and burn oil without losing compression. Run the test.