This episode marks the start of the running joke where Boyle inadvertently makes overly sexual/suggestive remarks or references without ever realizing how uncomfortable what he's saying is making others around him - usually Peralta; Boyle's almost never phased by it. The running joke continues throughout the close of the series.
"Full Boyle," the episode's title (and Boyle's emotional self-sabotage tendencies in matters of love) is a play on both the character's name and the common phrase's actual meaning. Being at "full boil" generally means to fully commit to an act or attitude, though it's usually used to describe a person expressing outrageous anger or rage. Boyle's tendency to go full boil into a romantic endeavor generally results in the Full Boyle.
The episode's title is spoken 9 times by characters. And also is the number of characters in the episode's title.