Trouble getting the decorative cover off engine

The stud is mounted to the plastic air intake as pictured. There would be no room to grab the stud from beneath. I would consider splitting the acorn nut.

 

That's a tough situation with no good access to that acorn nut. You could also try carefully slicing up the nut with one of those small, thin cutting wheels on a Dremel but you will need a steady hand and take your time cutting it to not slip and cut into the plastic cover. If worse comes to worst and you have to cut up the cover in order to remove it, Eurospares has a couple used ones for around $100 https://www.eurospares.com/Parts/159517/Ferrari?pi=111609 or there's a couple on eBay too so at least they are available.

 

I would remove all of the other nuts and pull up on the cover/ps reservoir while spinning it to try to pull the stud out. Even if you cut/break the cover, you'll still have to remove that nut and/or stud to get the ps reservoir off as it's sandwiched between the cover and intake. Interestingly, my car has nylocks and not acorns on the cover, which would make things a little easier, but doesn't look quite as nice.

 

Take the rear lid off then the access is much better

 

To Peter’s point, you might want to try a combination of pulling up on the cover with all the other nuts removed while using an impact gun to try to remove the nut

 

Put a vise grip on the nut and pull up while turning on the nut you could unthread the whole thing
Or maybe the stud is stripped and will come out anyway
Also remove fuel lines from that side and move out of way

 

Congrats on getting it off without damaging anything. Hopefully you can figure out why the stud was spinning in the first place and repairing it will be easy.

 

Nice