If you installed the correct wattage bulb in your new lamps as the original, the current draw will be the same! No way to make a filament bulb of the same watts and voltage draw less amps. Either you have new bulbs of lower wattage or something else in the system isn't right. Lower wattage equals fewer amps drawn on the circuit which may not trigger the relay. Stock wattage for the signal light bulbs is 21W. When everything is right - proper voltage, bulb, relay, ground = there is no need for resistors or anything else. The exception, of course, is LED bulbs. Since they draw only a fraction of the amps of filament bulbs, when installed in an older system you need to upgrade to an electronic flasher (relay). Your new bulbs are most likely lower wattage than the old flasher is designed for. A new electronic flasher should work and negate the need for resistors.