Weird Subaru MISFIRE After Engine Swap? (2.5 SOHC)

Owner of this 2008 Subaru Legacy says that he can't figure out why the replacement engine is MISFIRING on cylinder 4. He already tried a different injector, coil, and plug, with no change. From the driver's seat we can instantly tell that it's a COMPRESSION problem, but WHERE IS THE LEAK? And can we fix this Subaru "NPR" without buying any extra parts? NTS 500 DUAL CAMERA BORESCOPE: https://www.amazon.com/dp/B07SQ4FLYX?... THINKTOOL PROS: *****TOTAL $150 OFF!!*** https://www.amazon.com/dp/B08SWH2KP4?... Enjoy! Ivan