Okay to continue along that prior line of discussion briefly: it is totally possible to raise intake and exhaust flow without making more noise. And no, most people with i/h/e GSRs do not get 3-5 mpg worse than stock. They usually get about hte same mileage.

Engines make the most power when they are running lean which also produces less emissions. The thing is if you run too lean then you get detonation so typically car companies will make the stock ECU tune pretty rich to provide a margin of safety to account for the range of possibilities provided by manufacturing tolerances. So a modest increase in power through an ECU retune would most likely provide better mileage.

 

so is it likely that lotus will return the CPUs?

 

"Although the internals of the engine are standard Toyota (in fact made by Yamaha), Lotus fits different intake and exhaust systems and, significantly, has devised its own engine control electronics. The result is 190 horsepower (10 up on the Celica) at 7800 rpm and 133 pound-feet of torque at 6800 rpm."

http://www.caranddriver.com/article....rticle_id=7371