I've had sucess eliminating chrome from plastic RC car wheels with a 5:1 water/bleach solution and slow-boiling it on the stovetop for 20 mins or so. Make sure your plastic item doesn't sink and remain in contact with the bottom of the pan lest you melt it. Oh, and turn the vent on. Good luck!

Soaking chrome-plated plastic in bleach can remove the chrome. Soak the part in bleach.

A bit more mild remover is oven cleaner (spray and place in a plastic bag) or soak in an ammonia based household cleaner.

The bleach works fastest and the ammonia slowest. Ammonia might take a week. Bleach could work in a few hours, but is the harshest.

Shrimps alternatively you could hit it with some chrome spray paint.

Search on the words: chrome removal plastic caswell. You should find an answer in the results. You can leave out the term "caswell" for more results.

Kelley

Maybe Scotchbrite fine pad? It's flexible enough for the curve, you'd probably need to polish the plastic after to remove the scratches. Or do as I did and find a good used set on a popular online auction site for cheap. 

Anybody know how to strip off the remainder of the chrome finish from the fresh air vent?  Since the majority that once was seen is gone I'd like to remove the remainder for consistency.

Any suggestions?  Thanks.