Neither. It really doesn't work that well. It can do some cleaning and freed up a float in the gas tank of my MKZ (the fuel gauge used to takes minutes or even up to an hour to get to show full after filling up.) Other than that, was worthless...
It may help in some cases but the issue is that it is vastly overpriced. The MKZ is stilling showing below threshold on both (3) cats and I suspect it is more of a computer module issue. However, I was able to get my 06' Taurus to pass inspection, but the readings in my scanner shoot up and down but I can get it to pass at least short term. The CE light comes back on then will stay off for a while after reset.
Avoid the high priced cat cleaners that are pushing $30 for a 15 oz bottle. I would try Berryman's B12 before any of those, maybe a couple cans on a short half or 1/4 tank. The real bomb for me was Kano Kreen, that seemed to cut down the numbers short term. I also used a GDI intake cleaner that definitely helped as well. If you use the Kreen follow directions and try letting the car idle cold to op temp before driving out on the highway. You can reset the CEL then drive the reset procedure by finding the best way to reset Nissan modules and see if it comes close enough to pass. I think most can get most cars that are borderline threshold to pass inspection, but it might take some time and be frustrating and the CEL might well come back on but the point is to be legal for state inspections. A lot depends on why the cats are reading spoiled. They may be fine but the computer is off and you can try flashing it with a scanner or cutting the battery. Sometimes like my Taurus you drove it misfiring or needing a tune up which may have led to deposits. But removing deposits in the fuel system is maybe a first step and might help the cat(s). Good luck..
