I actually talked to that guy who did that, and he put two T-toosmall's (T25's) on his 4G63. He said it spooled better than a 20G and supplied the same CFM and boost. I was tempted to try it myself, but I came short on cash (as usual). I'm going to try a sequential T-25/14B with true dual exhaust system one day, if I get the chance. But, the reason behind using 1 turbo on a 4 cylinder is usually to keep costs down. (remember that 4 cylinder powered cars are usually cheaper and have fuel economy in mind) and the factory car doesn't need that much boost, so it's usually useless.

QuicknessNT