Since I allowed the Timeline app, a new face appears in my friends box.he never was there before...he shows up every other refresh.why

He's most likely showing up due to you viewing his profile (and possibly him viewing your profile/photos). Especially, since you say you view his profile regularly, yet have no other interactions.

And you're right, facebook has definitely changed it's friends algorithm on the new Timeline profile .vs the older Profile that has the friends list on the left-hand sidebar.

Here's some of the reasons why certain friends are now appearing in the 6 friends photo list box:
http://www.gotknowhow.com/answers/how-does-faceboo...

I have same issue after I swapped to timeline; a friend who I crush on and regularly check out his profile now appears very frequently in the friends box at the top.. Yet we never comment or post on each other's pages publicly or use the message function. I also notice people appearing who I suspect crush on me. Yet I never go to their page. I am hoping this means that my crush is also checking me out regularly. I know he does from things he has said ...but just how much?????