After jailbreaking your iPhone, iPod Touch or iPad on iOS 4.3.2 with PwnageTool or Redsn0w, you must install AppSync on your iDevice in order to install and sync cracked apps with iTunes. If you’ll not install AppSync, you will get Installation failed: Invalid IPA error in Installous and upon syncing your iDevice with iTunes, you will lose all of your installed cracked apps.
Steps to Install AppSync for iOS 4.3.2 Through Cydia:
1. Open Cydia on your jailbroken iPhone, iPod Touch or iPad.
2. Tap on the Manage tab at bottom and then tap on Sources section.
3. Tap on Edit button on the top-right and then tap on Add button on the top-left. Enter http://cydia.hackulo.us as Cydia/APT URL and click on Add Source button.
4. Wait while Cydia adds Hackulo.us repo and reloads its data.
5. Once done, tap on the Search tab at the bottom and type AppSync for OS 4.0+ in the search field.
6. Click on Install button on the top-right to install AppSync app.
7. Wait while Cydia downloads and installs AppSync on your iDevice.
Thats it. Feel free to try as many premium apps you want on your iDevice.
If for some reason, you are unable to install AppSync for 4.0+ from Hackulo.us repo, just download the AppSync DEB file from here and follow this guide to install it manually.