Yea its been done on the e90 post but still no DIY to speak of. Regardless if the 275 is attainable the 255hp of the si is very attainable and to have si numbers on an I and not have to pay insurance premiums is all good with me. The wiring is already their on our non si cars as you can see the two wires on the side of the manifold just swap manifolds and plug in the wires and you have an instant 10hp even without tune as the standard 3.0i has software built into the ecu to run the actuators so you can swap the intake manifolds and not even touch the ecu for a 10hp gain.
The 3 stage intake manifolds can be bought here for cheap
WWW.car-part.com theirs a fewvused ones for 200 bucks. 800 dollers cheaper than buying new.
More to come in a few weeks.