Dont start ya cycle till ya gyno has gone, and keep on the letro a little while after its gone to make sure its killed off.
Staying on letro that long will most likely cause rebound, so finish the letro and take some nolva to avoid rebound, then once ya systems clear start ya cycle.
Whats ya cycle ganna be?
Letro might be overkill as its VERY powerful and strips 80-90% of estrogen, and you need estrogen to help with gains. (check this thread)
http://forums.steroid.com/showthread.php?t=319202
Arimidex might be a better choice on cycle.