1991 944 turbo, failed nj emmissions inspection. it was origiinally only the hc and the nox, now its the nox hc and co. last time it failed i changed the cat converter and it passed with flying colors. when my 90 745 gle failed for nox i swaped the cats and it passed so i jus left it in there for about 6 months or so. the converter was bought new oem cali emmissions cat. before putting the cat in the nox was 1200 and the hc was at 1.82. co was way below passing. now with the other cat converter, nox is at 2900 when passing is 937, co is at 137 passing is 115, and hc is 2.8 and passing is .9. these are approx numbers, dun remember the exact ones. i dun understand why the numbers went up. what is changed so far is plugs (bosch plats), plug wires(oem volvo), and th o2 sensor is less then 2 years old(ngk). there are no obd codes. throttle has been cleaned and the cap and rotor is new. what is wrong with it? and is it something major? i dont want to go through this every time inspection comes up. the car has 150 k and i got it at 120k and since i got it the oil has been changed every 3k miles. the other thing is the turbo boost gauge never goes all the way to the left only about half way in the white section at idle, its been like that since i got it and i never though much of it. my uncles 765t goes all the way to the left then the car starts and is at idle. dont know mite have something to do with it.
thanks in advance
Jippi
P.S. sorry for the lengthy post. already searched the archives and the majority say its the cat converter.