While I don't have any direct experience with installing the larger 550 injectors, when I was considering that "upgrade" my research told me that no one had any good experience with installing them and getting the engine to run properly. All were running "pig rich". Everyone I found who had tried it gave up a went back to the OEM SRT6 injectors. Do some research here on the forum before you buy them . . . Just sayin' . . .