In addition to what has already been said, I own a 2000 SSEi and I have added NGK TR55 plugs, a tranny cooler, a K&N air filter and gutted the baffels out of my air bow and simply drilled some 3/4 in holes in the box, 180 thermostat, deleted the screen out of the */C, adjusted the */C to max boost at low RPM, Solid tranny mount up front, and added flowmaster 40'*. My average MPG on the interstate while driving from NC to WA state was about 24-27 and around town an average of about 20-22 roughly. My trip was in the summer and it ran at about 180 degrees consistantly. Also remember tire pressure can play a big part also in your MPG and the condition of your catalytic converter. My next thing i plan on doing is a high flow converter. I still have the stock pulley on it and want to do that also next. The PCM upgradeis a good investment also thru intense last I remembered (yet another upgrade I am planning on doing).