How many horespower do you guys think I am lossing from my exhaust leak from my cylinderhead and exhaust manifold, On the driver side, the rear bolt just sheard off clean?

 

Which bolt, the very last one? If so, if you upgraded to headers, those outer end bolts won't be reused anyway. Its hard to put a number on how much power you are losing, but if you have an exhaust leak bad enough to where you are noticing poor drivability and hurt fuel economy, then rest assured, I'm sure you are losing power as well.