What next for cylinder 3 misfire on my 2015 pickup after plug/coil swap?

[James.J]

My 2015 pickup truck has developed a persistent engine misfire, specifically in cylinder 3, that comes and goes but is getting worse. I've already replaced the spark plugs and ignition coil on that cylinder, which didn't fix it, and the check engine light is flashing under acceleration. I'm trying to diagnose it myself before taking it to a shop. What would be the next logical steps to check, like fuel injectors, compression, or a vacuum leak, and is there a way to narrow it down without expensive specialized diagnostic tools?