Too many trackers?

hi,

so i've been having some quite slow speeds recently (just a comment, not
criticism) and did what's been suggested and added the additional trackers
mentioned. sometimes this helps and the speed will jump from just 3 or 4 kb/s to
60+. great. but sometimes adding the additional trackers seems to make it go
slower!

can you have too many trackers listed? is there a point at which adding trackers
hinders rather than helps the download?

also, if utorrent reports that the tracker is offline, or its an unregistered
torrent, is it worth removing that tracker from the list for that particular
torrent, or does it make no difference?

thanks