I just went thru testing in denver I failed 3 times. I have a 03 wrx
My mods were
Borla header
Custom uppipe
Meagan 4 ' bellmouth Down pipe
Full n1 style 3 INCH exhaust
Aem short ram c.a. I
Stage 2 cobb map
Changed the down pipe to the double catted down pipe from perrin. And failed
Then went to stock map and the perrin pipe and failed
That time I was close here is the results.
Hc GPM 1.6264 limit 1.2000 fail
Co GPM 11.6048 limt 15.0000 pass
CO2 GPM 404.5305 pass
Nox GPM 3.3335 limit 132nd.5000
So I got a factory down pipe and loaded the stock map. new plugs and cleaned the maf sensor
and got the car real hot
And rolled in and passed
So in the end I spent about a thousand bucks got a ticket for no regi and paid the max fine at dmv for being 4 months late
Hope this helps
Oh ya btw emmisions testing is bull**** screw the ozone give me horsepower till the end.