When you swapped the freehub body did you remove the end cap from the Shimano freehub body you removed and replace it on the Campy freehub body? If you didn't you've created an expensive fixed gear hub. Easy to fix, just check the Shimano freehub body for the end cap, pop it out, place it on the end of the Campy, and you're good.
(Learned this from my own experience once when changing freehub bodies from Shim to Camp and forgot to move the end cap over by mistake).
I've just recently started using one of my Powertap wheelsets with a Campy 11sp. I did have to adjust the upper limit on the r.der. to prevent it pinging the spokes - just a smidge - and not sure if the rear was just off a bit or there's a bit of mismatch between the Powertap and Campy hubs/freehubs. Just an FWIW.
Another reason I like the Powertap so well; I can pop freehub bodies off, changing to one's with different gearing within a group brand, or from Shimano to Campy back/forth, quicker than the time it takes to remove and replace the rear skewer.