Broken exhaust manifold studs

[Bigshow]

A friend of mine has an 2008 like mine - he used my shop to rotate tires a few days ago and my employee noticed there was a broken exhaust stud on the truck. They checked the other side and there is one on each manifold thats broken. Is this common?
Truck is 2008, deleted, with H&S tunes on a Minimax...

 

[webb06]

Pretty common. Usually happens on back cylinders at least the ones Ive seen.