2nd turbo?

Hi, I'm the owner of a black 1996 850R wagon, and I'm thinking about putting in a second turbo, running in series with the stock one. A friend of mine pulled something similar with a Porsche, brought the compression up to some insane figures, and his car HAULS. I was leaning towards a second high-pressure Volvo one, any advice?

P.S. - The gray plastic on the trim strips has all cracked off, and it looks horrible. Is anyone else having this problem??