CAT C15 Acert Mxs/Nxs 660 Stock FileCAT c15 acert mxs nxs 660 stock file This is a file written for your stock c15 550 acert to add more power. The file has had the fuel turned up 20% and added 1 degree of timing to wake up your stock c15 acert. This is a non delete. A good file for when you want more power but do not want to delete your iva system. Works great with your factory 18 1 compression and is built for your 550 injectors.