the TDI 150 undertray is different from all other TDI's. Don't know exactly why, but needs to deal with FMIC and the car being 15mm lower.
Here's the undertray off my TDI 150 (not a pretty site, it needs to be replaced)
Compared to the undertray from my old TDI 110
The side bits have a cutout for the FMIC pancake pipe and are, I guess, shorter.
Sere Motors, who are an SCN sponsor, will give you a price for a new one.