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scott armstrong · 07-26-2002, 07:22 PM

about four months ago i installed a bassani hi-flow x pipe with cats on my 99 mustang gt. i have put on about 3500 miles since then and until two weeks ago had no problems. then the service engine soon light came on. i had the code scanned ( autozone does it for free,while ford wanted $97) it gave a 420 and 430. the codes stand for catalyst effiencey below threshold right side and left. Knowing that 96 and newer cars are very sensitive to exhaust mods, i purchased a set of MIL eliminators, however after installing them the light came back on two days later. the only thing that i can think of that could have caused this was the fact that a couple of days before the light orignally came on, i had filled up and added a can of STP total fuel system cleaner. has anyone else experianced a problem like this? does anyone have a suggestion on how to go about this??

thankx, scott

07-26-2002, 07:22 PM	#1
scott armstrong Registered Member Join Date: Jul 2002 Location: rockford,il Posts: 3	check engine light about four months ago i installed a bassani hi-flow x pipe with cats on my 99 mustang gt. i have put on about 3500 miles since then and until two weeks ago had no problems. then the service engine soon light came on. i had the code scanned ( autozone does it for free,while ford wanted $97) it gave a 420 and 430. the codes stand for catalyst effiencey below threshold right side and left. Knowing that 96 and newer cars are very sensitive to exhaust mods, i purchased a set of MIL eliminators, however after installing them the light came back on two days later. the only thing that i can think of that could have caused this was the fact that a couple of days before the light orignally came on, i had filled up and added a can of STP total fuel system cleaner. has anyone else experianced a problem like this? does anyone have a suggestion on how to go about this?? thankx, scott