in ca I'm subject to the tail pipe and visual inspection (among others) to pass smog. does the orientation of the exhaust components matter?

examples:

1. O2 sensor, Cat, muffler (current)
2. O2 sensor, glass pack, Cat, muffler
3. O2 sensor, resonator, Cat, muffler
4. y-pipe, super 10, O2, cat, muffler

the point is, the more "suppressive" the less measurable pollutants during the test, right? the last example is just something "WILD" I came up with on the spot. any input is good input. I DO KNOW about back pressure, just trying to beat the system until I find a pre smog donor

 

Number 1 will likely be the only accepted setup.

 

the cat has to be as close to the engine as possible or it won't get hot enough to do its job properly. if you need to replace your o2 sensor make sure you get a NTK brand one. if your truck wont pass smog you may want to look at your plenum gasket and possibly a bad cat/o2 sensor. i also always recommend running premium gas.

 

The state will want it in "as-built" configuration. Number 1 is pretty much your only option. You might consider testing your cat before you go in for inspection. If you have a temp gun, you can get your truck up to full operating temp, then measure the temp of the cat at the inlet and then the outlet. If the inlet side is drastically hotter than the outlet, you cat is plugged.

 

Also, adding more restriction anywhere other than by adding additional cats won't reduce your pollution, it will just make your truck wheezy.