have two broken manifold studs. one on each side. would this cause the check engine light to come on?

 

This could be, I doubt it though. I had my headers replaced due to rusted bolts/studs, but I had a HUGE exhaust leak. This made my truck through codes as the exhaust around the 02 sensors weren't getting "true" readings.

Had 'em replaced, code went away and truck just on average drove better.

So unless you have an exhaust leak associated with the rusted studs, keep looking. Also, which codes did the truck tell you? Keep us posted.