in the cases I've researched. I wouldn't say it's a wildly popular swap (especially since practically everyone except the U.S. already have/had an A4 TDI option; we just recently got the A3 TDI here), but there are some well-documented build threads out there with tons of useful info. The most attractive aspect to me is interchangability: TDI engine, one of the 1.8t engine mounts, 2.8l v6 transmission, 1.8t accessories, etc all bolt up perfectly and can be had for quite cheap.