I thought it could be a clunk line problem too but wouldn't the clunk be forced into it's normal attitude during an outside loop?(to the back and down) I also tested this by doing one while the tank was filled. It does the same thing. I said it was acting as if it was running rich but what it is actually doing is leaning out. I was expecting a few more hits than this, but I guess that means it is rare. I guess the only thing left to do is replace the lines as John said.