try the 3924 resister plugs first. if they're too warm step down to a 3923. msd's have to have resistance in the system; whether it's the wires, ballast or plugs, or combination. an ap3924 has 5000 ohns, regular 3924 7000 ohms; tested some rc12y's at 70,000 ohms! most resistor plugs will be 5000 or more ohms. of course non-resistor should be zero. if you're by-passing the ballast then more resistance will need to be in the plugs and wires.