Im not sure the AOS would cause your problems.

Sounds to me like something is disconnected, maybe even a coil pack. Are you 100% certain you put everything back together right, or maybe didn't knock something loose?

You know, I have had a brand new Bosch o2 sensor be bad right out of the box.....

Sounds fair to me, too.
Also, get the mechanic to remove the spark plugs and crank the engine over several times before he tries to start the engine back up after he replaces the AOS.

If there is enough oil in one of the cylinders, it can hydro-lock the cylinder, and break things you really don't want broken.

BC.

Porsche_Baller - did replacing the AOS solve your problem? I have a '99 Boxster and am getting similar fault codes. I also have a slight oil leak that looks like it's coming from the area of the AOS.