WANTED....Undertray

[Stickfinger]

what it says on the tin....XM undertray wanted

[White Exec]

I think these are now unobtainable, unless you can find one lurking somewhere.

Being more or less dead flat (on the 2.5, anyway), you could just make one from a sheet of c.4mm rigid HDPE or rigid rubber, cut to shape from your old one (if you still have the remains of it). The foam sound insulation on its top side isn't strictly necessary, as its main function is to prevent diesel racket from being heard outside the car by bystanders.

The fixing holes in the subframe can lose their threads over time, and moving up one thread size would sort that.