I know squat about building cars, but this has a few interesting notes about high-performance gas engine accessories:
Ten fastest production cars 5/13:
http://reviews.cnet.com/2300-10863_7-10016810.html
Numbers one and four use four turbochargers. Numbers two, three, six, seven, and eight use two turbochargers. Number five uses "a unique combination of a supercharger and turbocharger". Number 10 is a hybrid.