If an f-body were converted to a true dual system would that fail the visual emissions inspection? What about the sniffer. I like in Buck country, PA and I imagine my emissions standards are similar to most other places (save CA).

 

What year?

Federal law prohibits changing the number of cats or relocating the cat(s). For a 93-95, that left the factory with a single cat (except for the 95 CA emissions A4's), true duals would not be legal under Federal law. For the 96 and up dual-cat cars, as long as you don't relocate the cats, it should be possible to run true duals. But I'm not sure how effective the driver's side of the exhaust would be with the cat tucked up against the side of the engine in the stock location with the LT1. LS1 is a little easier to work around, since both cats are located further from the engine.

Then there's the issue of whether your state/locality enforces the Federal law - not all states do. Here in NJ, they do, but it comes down to whether they even bother to pop the hood, or whether the inspector knows if the car had one or two cats and where it/they were located originally.

 

a lil' off topic, but what about turbochargers? can you fail emissions for a turbo set up? since u have to modify the exhaust.