O2 heater circuit blows fuses immediately on start.

[kgkern01]

I just got done installing a cam/headers on my truck, and took my truck to my tuner.  We noticed that the O2’s weren’t reading and so checked the fuse and it was blown.  Put in a new fuse and it blew as soon as the key was turned.  Disconnected both O2 sensors and extensions at the factory plug, same thing, blew immediately.  I don’t visibly see any pinched wires.  Any suggestions?