Rough idle cylinder 1 code

What is your question?

Owned Yukon for 2 years and have put over $3000 of repairs in it. Engine light has been an issue from the start. Replaced right catalytic converter spark plugs wires just got it out of shop 3 days ago and light is back on and it’s idling rough. Mechanic flushed system and says there is a lot of gunk in oil-we’ve done oil changes on schedule. He thinks oil is getting past the rings on cylinder 1 but doesn’t know what else to do