From what you describe I deduct that you have an aircraft with EGT monitoring on 1 cylinder. It sounds like the other cylinders have reached peak and gone well on the lean side before the cylinder your instrument monitors reach peak.
This is not an instruction, just telling you what I would have told a student of mine in the same situation: Your only choice is to use the old ways... lean until it runs rough and then push it in until its smooth again plus whatever margin you want... and as always, stay below 75% effect and make sure to follow whatever instructions the manufacturer/manual, owner or operator tells you.