Having owned two 335ds during the past few years, I would definitely go in this direction! (Remember, 2 turbos are better than 1!!!)
Ridiculous power from a diesel plus great economy!
Personally, I would dump the 'run-flat' tyres and go for conventional set up, makes a lot of difference!
Also, I'm sure the 335 only comes in 6 speed auto?
Good luck and enjoy!!!