Hookup a small can of gas in the eng compartment to the pump inlet w a 5/16" neoprene hose and try it again. Still cutting out, open the hood and suspend a small container of gas high up from the hood latch like a bag of glucose on a hospital gurney and hook it to the carb inlet and try it yet again. EDIT reread the post and from the descrip it sure sounds like ign. I would check the plugs/wires. One of em might be defective and not be able to support the addt'l load between free revving and in gear. Is that on the road or foot braked in your driveway?