Some people pass others don't. AED told me some cars are more stubborn than others and that's basically it. Luckily most folks doing vehicle inspections don't make a whole ton of money so....
its hit or miss here, have had guys look and others that could care less...The lube type places are your best bet, the lube jockey|inspector in most cases is a kid that doesn't know his ass from a hole in the ground. On the other hand a inspector at a real shop is also likely to be a mechanic.
Ask some local Mustang, Camaro or Corvette guys....I'm sure somebody can point you in the right direction. Personally, I just keep an OEM h-pipe laying around just to pass.
Any county that touches Dallas County or Harris County (Houston) will have an emissions test that must be passed for inspection. All other counties are a visual inspection. Visuals are usually easy to get by with an offroad mid-pipe, but those counties touching Dallas or Harris will typically not pass the emissions test.
If you're in an emissions controlled county they will plug the car into their machine and you are not allowed to have any more than two sensors unavailable (depending on the year) If your tune shuts off the back two sensors, you may not pass.
I'm also in Ft. Worth, they will plug into the obdII and check for the sensors. It will depend on the shop you go to if they do a visual. I also agree that the lube places don't usually visually check.