Utica boiler ignition problem!

I purchased a Utica series MGB75 last heating season,from a local plumbing and heating contractor. My problem is that when the boiler lights there is usually a delay from the time the ignitor comes on and the burner lights causing a backflash when the gas ignites. The contractor has returned and attempted to solve the issue. they have been unsuccessful. They tell me the problem comes from the fact that the ignitor only lights one burner and the flame needs to cross over to the other burner.
Do you have any suggestions?