umm.... most likely your not gonna pass emissions unless your car runs amazingly clean and they dont do a visual inspection otherwise u need to get some cats to pass.
To answer your second question on whether there is a quiet midpipe....if you are going off road there isnt really no cats means alot of noise...the prochamber by mac is a little quieter then your standard offroad h and x pipes but other wise if you want a quiet midpipe keep the stock one
Even if you can pass the sniffer test you will fail the visual, easiest thing is to swap your stock pipe back on when you need to get it inspected. As for a quiet pipe o/r pipes, there really isnt one, their all pretty much louder then stock. However different companies have different sounding pipes.
Another option is a aftermarket catted pipe with only two cats. This will be quieter then the o/r pipe and should pass both the sniffer and visual inspection. Only downside is their in the 300-400 dollar range.
Here is my experience with getting the 2.3L N/A LX to pass emissions. Initially, the car had no cat.
All tests were done at the same Test Facility using the same Test Equipment. Test Operators did very however. Tested vehicle was an N/A 1987 Mustang Coupe. Mileage was 134,093 on first test, and 136,268 on final test (#4). Other than the Catalytic Converter being removed, the car was in good running order for first test and all other tests. No Diagnostic codes were present.
Baseline Test __________Tested____Limit_____Result HC Cruise___160______160______Pass HC Idle_____709______220______FAIL!!! CO Cruise___.51_______1.1______Pass CO Idle_____.54_______1.2______Pass Other than the lack of cats the car was in good running condition.
Re-Test #2 __________Tested____Limit_____Result HC Cruise___142______160______Pass HC Idle_____650______220______FAIL!!! CO Cruise___.51_______1.1______Pass CO Idle_____.48_______1.2______Pass Added New O2 Sensor, increased tire pressure to 52psi, disconnected fan to get engine hotter (good for reducing HC). Had run "Guaranteed to Pass" in previous tank (followed directions)
Re-Test #3 __________Tested____Limit_____Result HC Cruise___173______160______FAIL!!! HC Idle_____551______220______FAIL!!! CO Cruise___.53_______1.1______Pass CO Idle_____.61_______1.2______Pass Replaced Factory N/A short block with Used Factory Turbo Block; this was due to a hole in Piston #4. Plugged the fan back in.
Re-Test #4 __________Tested____Limit_____Result HC Cruise____44______160______Pass HC Idle______61______220______Pass CO Cruise___.06_______1.1______Pass CO Idle_____.04_______1.2______Pass A NEW Catalytic Converter from MagnaFlow had just been installed. At the time of the test, the cat had about 125 miles on it.
Jason's info is on track with what I've experienced. It isnt even so much how 'lean' of a tune you have or run, but you simply need the catalyzation from the cats' matrix/substrate.
I have a nice aftermarket catted-H on the '94 and the cats take away nothing from the sound of the exhaust (which I LOVE). Comparing aftermarket cats to the stockers is night and day in terms of restriction and noise (stocker is quiet).
I was gonna weld the old heat shields on my new midpipe to pass the visual. But if its real loud I don't want it, and if I can't pass emissions that does me no good either.
One of the reasons I asked, like someone said before, was the money for a catted midpipe. Looks like I'll be saving my pennies for a nice catted h or x pipe.
I used to have good luck getting my dad's no-cat 5.0 through emissions here in WA. We don't have a visual inspection here which made it easier. It always just barely squeaked by. Then they started using the dyno's again, and last time I tried it didn't pass. I just threw the stock h-pipe back on and called it good, I don't want to be swapping it every couple years.
The next h-pipe I buy will definitely be a catted H or X. Unfortunately that will be a while since they are so expensive.
It's pretty clear from Jason's info that a good working cat really cleans up emissions.