My Autech had no extra bracing around the "C" pillar, i was under the impression there was something there to but nothing. All the bracing under the floor bolts striaght up to a standard RS4.
The holes for the intercooler piping on mine had been done with a hole saw and a drill, nothing to rough about it. We just did the same with the swap. There was alot of mods to the panel under the rad support that i could see, little trimming and enlarging of holes, also the ends of the chassis rail are trimmed back for the blow off valve return pipe.
None of it looked "aftermarket" was all done like factory.
And yes all autech's are plated as a RB25.