I found the 50mm piping to get caught at full lock but it was just a tad fatter than the pancake pipe by a few mm, but rubbing was never a major issue as i did nothing damaging to the pipe long term, you wouldn't have noticed wither until you had a look under the wheel. Plus the majority of the 1.8t engines piping is 50mm.
Wouldn't be able to advice you on egr's as I don't have a diesel.