Although I'm still researching here's what I've gleaned so far.
Constructive Objections encouraged.

Practicalities
You can go for an Audi S4 82mm TB PN077133062A for $150-$200 (2nd hnd). Plenty of them around.
You need to rewire the pinouts and maybe add a connector.
I'd seriously consider getting some work done on it also - like shaft/porting and polishing.

To reap full benefit you need to change your SC snout to the post 2006 SL55 type of PN1131400912
That also will need to be ported and polished and the bypass valve plated/smoothed/streamlined for our application (no bypass).
Then you need a 6mm adapter plate between the SC inlet and the TB.

Then of course comes the Y-Piece and intakes.
I understand an 80mm PN 1130900329 will do it,
but intake suppliers may come to your rescue here with a suitable 82mm Y-piece to fit to their DCAI.
But you can work your own around the 1130900329 if you're up to it. But it has oval outlet hoses....so tricky.

Performance gains....
My calcs suggest maybe 4-5rwhp on an SLK32 61/155 setup since you gain an extra maybe 0.5psi at WOT. But given the DCAI is adding 7-10rwhp (and reportedly better low end improvements), that's not a shabby extra if you can DIY it cheap enuf.
The E55/SLK55 guys are talking it up. EC is even claiming 40rwhp on their website for the 55's....I cant see it - breathing must be a particularly weak link in them if that is the case.
here
Given our 61/155 setups with a few other mods are nearing the stock 55 cfm, I would imagine our efforts maybe similarly rewarded.