Hindsight

So my 04 S4 won't pass emmissions because the computer keeps coming up as "not ready". I've driven it hundreds of miles, highway, city etc. Now it's at the stealer. They've had it for several days and can't figure it out. First they thought it was the o2 sensors, then they thought it was the spark plugs.... not sure where they are at with it now. This is starting to make me nervous.

Have any of you encountered this issue?