An optical mosfet will not do shit for your feeding, may fix the double shots, but feeding no. The delay chip should help with that. I would look to see if your tappet plate is in good shape. I would also shorten the tappet spring to increase the return pressure. Look at the nozzle to make sure that it is cycling properly. I have a hunch you are using midcaps right? If so then it sounds like midcap syndrome. Check the cutoff, I doubt that is the problem, but a worn one can make double feeding occur.