Thanks for your reply. The original symptoms were as follows: Reduction in mileage, reduction in power, smoking out exhaust, missing, very strong smell.

I concluded that the car was running extremely rich. There was no air pump noise as has been described by many others. The car still ran ok at high speed but with less acceleration. (I had to get home from a trip. )

When I took the car in to the Volvo dealer in Hyannis MA, the check engine light was not on, but they said they found 15 codes. I am trying to get a list of these, but do not have it yet.

I have all of the parts that they replaced which included the air pump, check valve, 2 oxygen sensors and a barometric pressure sensor. Is there an objective testing place that can see if these parts are really faulty?

Again, thanks for your help.