The180 t-stat will hurt MPG as the computer will dump more fuel since the CTS says the engine is not warmed up. Altering the TPS will not do anything because it zeros at whatever it was at when the engine is started. The V8 throttle body will not help bcause the O2 sensor will reset the map when it sees the extra air to keep the A/F ratiothe same. The bigger TB will allow you to make a tad more HP at WOT bcause the injector pulse is not going off the O2 at WOT, it will have a fixed injector pulse so it wll lean it out by letting in more air.