So the ole geo is having an issue that I can't figure out. Once it gets warm it starts cutting out almost like someone is turning the ignition on and off rapidly. Buuut, it only does it under a load and in 4th and 5th gear. I can drop into 3rd and floor it with no issue, as soon as i shift into 4th no bueno. Has new cap, rotor, plugs, wires, and fuel filter. Any ideas?