Does this sound normal?

And regardless of whether the flapper valve is actually there....the holes for the shaft probably are and need to be plugged.....or repaired if you wanna go that route. You can get new bushings and repair the heat riser if that's how you wanna do it. I've always just removed the valve and plugged the holes. At any rate, If you remove the manifold, wherever it's leakin should be obvious from the carbon trail the leak has left. I would remove it again and LOOK at it very closely. You'll find it.