with my Acura RDX, i just played with the ECU...I only get 7 psi of boost now vs 14 peak to better match the efficiency map. I don't have the map for it but it looks something like this:
This way i can also run stoich (leaner now) until 3500rpm. Stock car used to enrich mixture depending on how much boost. Ignition has been advanced but that's on the engine side not the turbo. I saw no reason to change out the turbo though, because the stock turbo is pretty good with the variable gemetry design and all. overall though if it was up to me, i would totally just avoid turbochargers. Toyota experimented with that for the toyota prius and in the end they decided to go the NA route.