Plastic undertray at the back..

[85db]

How important is it? Mine is hanging off so I'm tempted to just take it off rather than try to fix it as it doesn't look in very good shape. But on the other hand it must be there for a reason, so I don't really want to take it off if it will cause further problems.

[AndyM]

Lots of existing topics on this so worth a search for more detail, but essentially it's up to you.

Many people have removed them without ill effects, while some like the look or feel that it provides useful weather protection and keep them on.

[spit]

They offer an element of weather protection but they're not essential for reasons of mechanics or aerodynamics etc. Cosmetically its a judgement call whether the car is better with or without!

The Japanese domestic MR-S never had undertray parts. Later import SVAs required them to be fitted and many garages kept a set purely to get through the test, after which they were removed for the next one.

If your front half is intact I'd be inclined to leave that on and lose the rear portion.