I don't know how long it would take for a quote. You would just have to call them and set up an appointment. Or tell me what you need done and I will ask. The O2 sensor doesn't look like it would be difficult to replace at all. I think the 400E only has one. You just have to unplug the harness and use a wrench to unbolt the probe from the exhaust pipe. Some people can tell by just smelling the exhaust which I don't recommend for extended periods of time. Another way is through a probe in the exhaust which is essentially what the emissions test is. You will need something up stream though. I have an air to fuel ratio meter in my car but I assume that you can trust the car's computer to a certain extent. At any shop that works on mercedes they can access the A/F ratios through the main diagnostic computer.

I really don't know how they determine when a cat is bad.

Do a search for Rainbow brand speakers.

Sixto
95 S420
87 300SDL

Also keep in mind that if it is crackling from an entire side or one side not working etc. it is probably an amp not speakers. Actually the stock speakers with a decent head unit and a sub is not too bad.

I have now failed VA state emissions twice now. After the first time I bought this emissions solution, used that and drove the car plently. I brought the car in hot to get tested (first time was cold) and the numbers are almost identical. Please look these over and throw me some sort of help. (Tune-up was done recently)

================== Test 1 =============Test 2
========= IDLE 2500 ===== IDLE 2500
====== Limit Reading Reading Reading Reading
HC ppm 125 555 351 553 283
CO % --- 1 7.65 4.39 7.53 3.53

I was thinking it could be the O2 sensor, but I think that will only help CO2. Please post anything that might help, I'm desperate!

High HCs is very frequently the result of a tired O2 sensor. Could also be a problem with how the engine responds to the O2 sensor signal. Do you know when the O2 sensor was last changed? 160K miles is a very long life for an O2 sensor.

Sixto
95 S420
87 300SDL