i had a similar problem. the longer and more pb u spray on it the better. it wouldnt come off for the life of me. my ex's father suggested i soak it in pb. let it sit overnight and try again the next day, while spraying it every few hours with more so it seeps in better. try that. and trust, its a lot better than drilling and tapping an exhaust stud.. which i also had to do... so dont break that fucking thing.