IPod touch purchases?

Just wondering if I restore my iPod... I need to update the software, and some stuff is making the iPod buggy... If all my in-app purchases will be deleted, even if I sync it. I know the iTunes and app store purchases will sync, but will in-app purchases, like tap tap revenge songs that I have bought inside the tap tap revenge app, also sync??? I just don't want to lose anything if I restore. 10 pts to best answer!!!! Thanks