Missing Part on Right side of Engine. Should I Be Worried?

[T.vulgaris]

Hello,

I just picked up my first Saab, a 2003 9-5 Aero Wagon. While doing some basic maintenance to it, I discovered a spot on the head that looks to be missing a part. I'll let the pictures speak for themselves.

What is this part, and should I concern myself with finding a replacement? I've had no luck finding my answer online through search engines or parts store catalogues. The car is otherwise running well at 153k miles, with the only OBDII code found being a pending P0455 that I believe I've already remedied.

Edit: due to the "Similar Threads" section under this thread I actually found my answer in a thread from 2015!

[ChipSquirrel]

Hi There!
Not really, but depend's...
Is your Aero an auto or manual box?
Cheer's!