Could a bad coil be causing me to backfire under a load. Have checked my timing. Have a new distributor, cap, rotor, wires,spark plugs and ecu. With my timing light on every now and then the light misses the mark. Runs great unless i gas it going up hill with the rpm's low (under a load). Havn't changed coil, could it be my coil? Would like to eliminate the possibility of it being a problem with the ignition side before moving to fuel issues.