Thanks everyone for the diagnosis/suggestions. I will pull the tank and run new fuel line. Bill, this was something that I thought about initially, however the air in the line is only evident when the plane is oriented vertically. If foaming is the problem, do you think it would be apparent when the plane is sitting level? Also, I have the tank wrapped in foam and slid into the fuse for a snug fit...a very snug fit. I suppose the fit is tight to the point that it may be defeating the cushioning effects of the foam as it is compressed very tightly. I am using an 8 oz. tank and aside from going to a smaller tank, I don't see any way around this except to maybe try a Great Planes or Hayes 8 oz. tank. As mentioned before, aside from the cutout with the plane vertical, the engine runs impressively. I will check the line, fittings etc. to see if the problem is cured. Thanks again.

Steve