hey OP, congrats on the gains.
I'm sure there's a load of very good and effective pull up plans out there on the interwebs. I used this one a couple of years ago and found it very effective.
http://physicalliving.com/how-to-rap...onths-or-less/
the 'grease the groove' approach is something I still use now (actually did 12 sets, not to failure this morning)
Of course, losing more weight also makes a huge difference, but I found the formula listed in the above link worked really well