2001 Blazer

Been working on a 2001 Chevy blazer. just finished repairing brake line and now has a P0300 random misfire code. I replaced with plug wires and plugs, it had been 5 years since change and is running good, fires right up but i think the code is going to come back on. We’ll see. had two more codes to work on but want to cover all bases to get the P0300 out first. Have done plenty of misfire, cylinder 3 or 4 but random misfire hard to pinpoint. any suggestions.