Perry,
You could try searching (that input box at the top right next to the magnifying glass..) under wig-wag for a post I put in a while back. Helps reduce 'burp' and getting in a first flight w/o starving or richening off the engine.
The reason for the burp may be related to the change of g-loading when the model kicks over from inside g to outside g at the intersection in the figure eights. Why it takes the form of an audible misfire or non-fire for some Fox 35s could be a very complicated combination of many things. If the tank, prop, plug and fuel are all good, and the setting is about right, you may hear a one or two step stutter without losing noticeable power, and without the engine shutting off.
The low round loops in the round Eights require about 10 to 11g for their shape, and the effect of gravity adds 1g at the bottoms and about 3/4 g at the top (trigonometry - at the angle that gravity works on the model at 45° line elevation.) The intersections are supposed to be vertical, so lift and gravity are at right angles - they don't interact at that split second... So the loads on the fuel are from 10-11g toward the wheels (in the inside) to the same range away from the wheels (in the outside) and that's suppossed to happen in a hundredth of a second or less. Quite a change.