Since you do not have a 3Gs, then you have options other than AppSync. If you have trouble using AppSync, then try Installd. It does the same thing using a different method. Installd patches the installd file, whereas AppSync replaces the installd file with a modified version of it (this sometimes results in quirky behavior). You can get Installd from Cydia by adding this source:
If you still have AppSync installed, be sure to uninstall it first so it will replace the modified file with the original unpatched file. When installing AppSync or Installd, always install it independantly and RESTART IMMEDIATELY AFTER INSTALL.