Ok, did some more talking with the local engine guru, and he suggested that the pressure tap was in a bad spot, and in high g moves there wasn't enough pressure on the tank to overcome the g forces. It was suggested to move the pressure tap out on the muffler isntead of the manifold, right where the muffler starts to narrow. Since this is a point of restriction, you would, in theory, get more backpressure. Does any of this make sense? Doesn't take much to drill a hole and tap it, and even easier to put a plug in, but I was just curious as to what you guys think.