Originally Posted by wstar

It's going to vary by state, I know nothing about NJ. Here in TX you can generally get away with reprogramming around the CEL (as in, actually reprogramming the ECU), but just "clearing" it with a simple code-scanner won't usually cut it (because the OBD-II info the emissions testing place looks at shows whether a complete drive cycle has been performed since the last code clear, and they want to see it showing completed and free of codes). There's no inspection for the first 2 years on a new car though, so in TX you'd have two years to find an ECU solution before you ran into that issue.


Technically, even in TX, I think test pipes are illegal on public streets, but if you can suppress the codes with an ECU flash, you'll probably get away with it since many inspection places only care about the OBD-II readout.
I went the HFC route because at the time I was making the decision there was no ECU flashing available for the car at all yet, and I didn't want to be fighting clearing the codes all the time until one became available (having a CEL thrown randomly while you're driving and not knowing what it is sucks, gotta shut down, get out the scanner, confirm it's the O2, clear it, wait for it to happen again...).

Once I get an ECU flash going that can suppress the CELs effectively, I may decide to swap my HFCs for Test Pipes at that point, if the rasp isn't too bad (maybe resonated ones would help).