I would personally on a std coil put the gap at 0.6mm, check the voltage at the pump under load, but also check the fuel pressure is correct, for around £35-£40 you'll notice quite an improvement in response lower down and smoothness with a "group a coil".
Pumps have had sometimes 6-8volts at pump under load due to old wiring, 2 must do's on a cossie are fan rewire and pump rewire, asking for trouble and expense if these two not done as a minimum.
tabetha