Interesting post,
Im normally found on the s3 forums and have do hybrid turbos for s3's and TTs i have my own range of hybrids.
I bought a BFB a4 1.8t avant about 3 months ago with the purpose of building a hybrid turbo for the a4 longitudinal engine. I've been in discussion with a few members on here to figure the feasibility of such a turbo as there isn't really A high performance Turbo for the A4 with a "stock " fitment.
With all this in mind I have a finished version of the hybrid made up and hopefully in the near future will be fitting it. Its based on the k04 turbine from the s3/TT and the 2280 compressor wheel . This combo is capable on paper for 300 bhp but think its going to be limited by the restrictive turbine housing. To assist this a tubular exhaust manifold will be fitted, Fmic and 3" tip/maf and downpipe and decat. There is a future plan to aim to fit one of the k04 hybrids to the a4 which could yield 320+ bhp but this is a distant project.
With any luck I plan on starting the build in the next month or so and potentially could offer a full package but will certainly list all items used and map for the BFB as most of the parts bar the turbo are off the shelf items.
But back to your post, 250bhp from the BFB with out a turbo upgrade isn't going to happen, the available hybrids on the market will see you get 260bhp going BT route will see you as much as you want and can afford otherwise your just looking at a remap, Fmic exhaust and 230bhp is really your max from the BFB as is.