(blah)
I'm not a tree hugger and I'm not trying to scare people. Just presenting the facts. People are free to make their own decisions but it should be an informed decision. Bypassing/removing emission controls is a federal crime, plain and simple.
Do people do it anyway? Yep.
Do people get caught? Not very often. Automobiles only produce about 25% of air pollution, so the EPA considers tuners "small potatoes".
Do shops get caught? Yep. Last I heard, the fine for a business removing a cat was $10,000.
You are right about one thing, though. The EPA will not consider any modification to be a violation of federal law if there is a reasonable basis that emissions are not adversely affected. So if you can pass emissions without the second cat, then you're fine! (thumb)
Don't take my word for it, though. Visit the EPA's web site and see for yourself.
http://www.epa.gov
Specifically this document:
http://www.epa.gov/Compliance/resources/policies/civil/caa/mobile/tamper-memo1a.pdf
Also, most states have additional laws against tampering with emission controls. Here's a good EPA-based guideline from the state of Texas' web site:
http://www.tnrcc.state.tx.us/air/ms/tampering.html
I'm sure other states have similar guidlines.