Hey Michael,
Have no insight as to engine cleaners. Buy what is on sale? Watch for
cleaners that dissolve Asphalt/Blacktop if one is parked on same, during the
cleaning. Personally, being a bit on the anal side, the cleaning product is
less important than the 'elbow grease' applied by the user, if you catch my
drift here?
Glad the hear you are satisfied with your new Nokians! What model are you
running? I installed the WR model  last winter. Great improvement
winter/summer/wet/snow/ice than the Yoko's they replaced.