Would it be possible to replace the 2.0 TDI engine with a 3.0 TDI in a a4 2007
Guess it depends upon a number of factors, technically the car is a big mecano kit and as the manufacturer already offers that engine in the bodyshell you already have, its just a case of sourcing all of the bits that go with the 3.0 tdi lump and tranny.
If you were hell bent on doing this, would the best way to approach the project with a salvaged 3.0 tdi engined car - one that had a rear end shunt would be ideal ? That way you could (hopefully) have all the bits you need (the list gets longer as I think about it!) to hand........... The question remains on resources available; skill set, time, facilities and space to complete the work etc etc and of course the money.
If it were me (and I know your not obviously !) I would be with Karl in so much as I'd sell my existing car and buy an original 3.0 tdi of the same spec (or better) than I already had, but thats cos I wouldn't wish to dedicate my resources that type of project (I have too many concurrent 4 wheeled projects underway as it is !!)
But echoing Giosabcsi, I'd say if thats what you'd like to build, then go for it, and I'll be pleased and interested to follow your build thread !
Which ever way you decide, good luck and all the best !!
Gary