I have a 1993 300E (M104 motor) that is almost 6 months out of registration... and I'm still trying to get the F****** to pass! I had the head gasket replaced so I have new plugs and wires... all my vacuum leaks were fixed, new 02 sensor, tried the PASS SMOG "snake oil?"... have a new EGR valve and am waiting for delivery of my EGR exhaust return line because the existing one is plugged (but I heard the EGR has nothing to do with HC's, which were high on my car)... so hopefully the EGR solenoid is still good...
I have new tires, brakes, water pump, top end... it's a great car... but SH**!!!
So no noise at all from the CAT pretty much means that's not the culprit...
WHAT gives???
What do you think helped you pass smog?
THanks!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)