Header Leak??

Did you torque the bolts to spec, or just tighten them by hand?

Try torquing them to spec if you just did it by hand.

(I know a couple of bolts cannot be reached with a torque wrench. What I do then is to torque one of the easy ones that I can get the torque wrench on, and then go back and see how much force it takes to turn them just a little bit, then go to the hard to reach one and give it the same force of pull... It's like trying to calibrate your hand...)