#1 exhaust valve blow-by?

I heard what I thought was a ticking sound coming from #1 cylinder area. I put my hand in front of the valve cover and realized it was a hissing noise, and I felt air pushing it's way out from under the outer front corner of the valve cover. I removed it to confirm that, and took a video of this problem. I've never experienced this, so I made sure the oil & water weren't mixing to eliminate a blown head gasket issue. I'm gonna get a compression tester and test #1 cylinder. When the engine is running the air bursts do come from the exhaust valve, and the engine seems slightly sluggish when driving. The exhaust looks normal out back also. I feel certain the exhaust manifold gasket is not the source. As usual, I am open to suggestions and theories.

Well the morning sunshine revealed it is a failed exhaust manifold gasket. Black exhaust soot can be seen on the head, in front of the #1 exhaust port at the header flange. There is no exhaust soot under the valve cover on the head. My exhaust system is all welded so it is gonna be a chore to repair.