I've done quite a bit of tuning in the past myself. I adamantly agree with you that on a stock engine, playing with tuning can get you maybe 20-30% more fuel economy, but possibly at the expense of increased emissions. I've been fortunate to have access -- and the means to test various technologies over the past few decades. Usually we would start with a stock engine and maximize it. This became OUR baseline. Then we would add some technology and retest without retuning. Then we would play with the tuning to see what it liked. Emissions testing has been an integral part of this process all along. (Twenty+ years ago I was using a 4-gas analyzer. For the past several years I've used a 5-gas.)
Based on that experience, I'm not much of an advocate of these "
tuner modules" that report to improve your stock engine efficiency by some notable amount. I
AM an advocate of improving on what the factory did mechanically (think
Combustion Efficiency), then go to tuning to get the mechanical gains working with the software. There have been so many different technologies I've tested that I could
prove improved what goes on inside the combustion chamber, but the factory ECU would only tolerate a slight amount of improvement then default to "gas guzzling mode" (for lack of better term).
I suppose if you firmly believe that the OEM's are delivering the best fuel economy and performance they know how to provide, then there's nothing I can say, link to, or post pictures of that will change your mind. HOWEVER, if you realize the OEM's hands are tied -- by not only the US EPA and CARB , but also other governmental agencies, all of which must be funded somehow, and willingly receive contributions from entities that stand to benefit from legislation -- you may realize that science has the ability to virtually eliminate harmful pollutants while simultaneously raising the engine's efficiency from a paltry 20% to a more reasonable 60% (or much more!). That fair and reasonable step triples fuel economy at the engine level! After all, 60% efficiency is NEVER considered out of the realm of probable -- even factoring in Faraday's Laws!