As stated above the class hasn't changed much, I have used that in the past with 3.6 and it still works. You can find the class details listed in: vBulletin 3.7 Code Documentation and then see if you are going wrong somewhere.
If all else fails, find where vBulletin parses it's posts/signatures and see how it is done in the default vBulletin code. Then just mimic what has been done.