I found one of my pr6 site ,have many backlink pages that have 100+ outbound links. so one question I must solved: do these page that link to my site contribute to pr? if I remove all these kinds of links, my pr will remain pr6,right? more, should any effort be put these pages link exchanges? if yes, the will save huge time and effort.I WILL focus on exchaging link with page that have no more 100+ outound links.