my cars previous owner installed a 3" divorced waste gate catless downpipe and exhaust. no resonator just a muffler.
he was having trouble passing state inspection because a visible cat must be present to pass. even though we dont have emissions in my county, emissions and state inspection are separate. some counties in pa dont have emissions and some do but all must pass pa state safety inspection.
to pass he installed a 3" hi flow race cat BUT the problem is he had the exhaust shop install it AFTER the down stream o2 sensor.
so the cat is doing absolutely nothing except adding un needed back pressure.
the downstream o2 is getting a reading as if the car was catless anyway...
my solution is going to be this. itll be "catless" and run well with my tune and also pass visual state inspection.
i found out about the bad 02 readings when i decided one day to flash my car back to stg 1 map and i instantly got a CEL for un calibrated 02
p.s. my car is an 04 sti and it has a accessport stg 2 tune for catless. and i tweaked it a little for my 2mm bigger maf housing and intake.
i cant speak for everyone else but im pretty sure catless subarus have no problem passing emissions/smog tests in other counties in pa