Can a faulty exhaust manifold cause you to run a little higher engine temp than normal?

 

Define "faulty exhaust manifold" (holes/leaking vs restrictive) and "a little higher engine temp than normal." Also how bad is the manifold.

 

Manifold looks fine from what I can see, no crackes, etc. I just ask this since I installed headers I noticed a cooler running motor. Not a drastic change but its there. The headers I have are stainless steel shorty's.