[Robin_NL]

Originally Posted by grimlock

Without knowledge of the way the N20 is actually built, or having real samples of failures from over-boost, its hard to say definitively the N20 is more stressed.

But can still assume that, given the same (ok, who knows what is actually different?) N20 sits in both the 320i and 328, one giving 17x hp and one 245hp.
I think its a better idea to tune the 320i up to 328 levels.
Would I boost the 328i to ~300hp? -Sure, if you like sitting by the side of the road.
A hp/L comparison is only cursory/general given lack of knowledge of the specifics of how the engine is built.
If I got the 328i I wouldn't feel safe boosting it.
If I got the 335i I wouldn't feel risky getting 350-360hp from it.

btw. you can boost to get any HP number you want, my friend keeps telling me how he gets 500hp from his audi 2.0T.. but he's also on his 4th engine. At least that's what he tells me.