P0303 code 2010 silverado. Reoccurring

Reoccurring misfire code on cylinder 3. Changed the injector spark plug and swapped the coils from cylinder 3 and 1

Oh it has good compression and I run seafoam

Here’s some ideas

Hook up a spark tester to #3 coil

Hook up a noid light to #3 injector

Please post back with results

What does “good” compression mean? I.e. what is the actual psi on #3? And on the others?

Which engine is in it?