Cylinder 3 misfire

[diamondphorses94]

So I purchased a 2016 Ram 1500 with the 5.7 engine Saturday from a dealership. Got this truck on a good deal. The miles were 200000 but upon looking vehicle had been regularly serviced and maintained. Take it home and am getting the P0303 code. Yikes 😬. So first and foremost I changed plugs and replaced coil. Checked compression. I got 120 psi. So I then take it to a local mechanic who checks pressure gets 50 psi and states that new engine needs to be installed. I have added sea foam to both fuel and oil and going to change oil within 200 miles. I’m going to remove valve cover to inspect springs and lifters, push rods. Also going to use bore scope to inspect piston cylinder walls as well as valves. I’m hoping this is going to be this case and have a valve issue. Anyone have any other advice? Thanks

 

[Autoplay]

Replace fuel injector

 

[diamondphorses94]

Replace fuel injector

I should have also noted the mechanic I took this to swapped and still code stayed within cylinder 3. Or so was said. I could swap it out just to cross it off.