I would recommend
not running your engine lean of peak without an engine analyzer. I wouldn't be without the EDM-700 I bought for my continental TSIO-360-FB.
Run rich of peak if you are restricted to just an EGT guage. Just because the engine runs smoothly lean of peak does not mean you are not causing damage.
www.piperowner.org is where you will find excellent advice from other Dakota owners with Lycoming experience.