hi, have an '85 OMC 305 5.0 liter with just rebuilt rochester quadrajet and new coil. Engine runs fine at low speed 5-10 mph but when going faster engine out of blue does a surge back and dies; takes a little cranking and pumping of throttle to get it started again but then runs fine again at low speed but did same thing whaen going a little faster. engine has pertronix module and was just tuned up and timing set to specs.