I will suggest what worked for me. Drive around for a few days with it installed. Try using a slide-hammer while the exhaust is moderately warm.
myoung, if you can't get your hands on a slide-hammer, take a trip over to AutoZone. They have a FREE tool rental program. And guess what... they rent slide hammers! Surprisingly the down payment is only like $20, and it is returned to you in full once you return the tool. Might as well give it a try, can't let that thing sit stuck in there forever (and its free!).