iPhone 5 syncing with 2 macs problem

When I got my iphone 5, I was leaving for vacation, so I backed up my old phone to my macbook pro and took off. I then restored it from the MBP backup, intending to switch back to iMac syncing when I got home a week later.

When I got home, I backed up on both machines, then did a sync on the iMac and it looked like every thing was fine. Now, 3 days later, I see that apps are not updating, so I look in settings and I see that my iTunes wifi sync is set up to sync apps to the MBP and everything else to the iMac. (I use icloud and imatch).

Anyone have any idea how to switch the app sync to the iMac? Short of doing yet another back up and restore???

Thanks

Tom