I am glad you are observing Lenten practices! They are very rewarding!!
They are certainly difficult, but that's what gives us discipline. It is also a certain kind of sharing in the suffering of Christ.
I would suggest that you try not to give in to the temptation. Maybe limit the time gradually. But don't set unrealistic goals. You'll end up in frustration. But don't go too easy on yourself, either. Limit your time gradually. When you want to get on IM, go and read about history, the Bible, or some subject that interests you. Chatrooms can take up so much time, and it's really not good for our spiritual lives sometimes. Take advantage of the "extra" time, and use it to improve your mind and spiritual life!
Hope this helps!