I am ranking 2nd position for a high traffic keyword phrase, my title only has 2 of the 4 words in the keyword phrase.
I’m thinking of changing the title to match the keyword phrase more exactly. What are your thoughts? Good Idea / Bad idea? I’m mainly trying to jump from 2 to 1 and definitely don’t want to lose rankings.
If I had #2 position I wouldn’t worry about it.
I’m not an SEO expert so unless you are sure making changes won’t drop your ranking then go ahead and try it. But if in doubt, then why risk it unless there is a prize for getting #1 
Basically:
If it ain’t broken, don’t fix it …!!!
I would agree with you except for this:
I had a #1 position for about 3 months and my traffic went up about 20% just from switching from a #2 position to a #1 position, 20% increase is worth what it’ll take to get up there.
You can add the other 2 words to your title it might or might not make a difference doubt you will drop or increase. Unless you add more to your content, by make it more bold, italic, a some H-tag titiles. Also what i do a lot is simply create another page with the other title and add new content (make sure not to duplicate) and link both pages to each other.
hmm… For me #02 Position on Goolge is quiet good. But if you change your title , than it can be helpful in maintaining your rank as well as boosting your rank.