dont know about the engine failure as I was running a dump pipe and cat before I got my tune, but when I got mine done it brought the check engine light on and when I checked the code it was cat efficiency. With the progressive learning computer in the FG series it recognised that my cat was less efficent than before and put the warning on ( lucky I have the x-cal 2 flash tuner and I can remove the fault light and got the handpiece reprogrammed to eliminate the problem. And yeh, keep the heat sheilds on mate.