Get error code P0302 New plugs Check spark. OK Check Injector, OK PSI 50 in Cyl

Hello, 50 PSI in the cylinder definitely shows that the cylinder could be low in compression. Low compression would indeed result in poor engine performance and a misfire from that cylinder. Unfortunately, further testing needs to be performed to determine if you have an issue with the base engine or instead with the cylinder head. You may also want to compare pressures across all cylinders to see how low the one in question is in relation to the rest.