what is meant by "spark plug non-foulers so you don't trip a CEL."

 

On other cars they are great because they cut out that nasty rasp that is associated with removing the cat sometimes (ex. on a 350z), but on the S2K this really isn't a problem so resonated testpipes aren't needed. Why I say to stay away from them is because Megan makes resonated testpipes that actually start to sound like a rattle after very little use. A local member already went through two of them, they are crap.