A lot of us stick with simple things. As mentioned, aerodynamic changes, gearing, more elbow grease than messing with ECUs. You are welcome to do some searches, which surely you are familiar with seeing your experience here (since 2009, impressive!).
Some recent ECU tuning showing great results can be seen here:
http://ecomodder.com/forum/showthrea...ild-26722.html
I understand you have high expectations, but your writing seems like it has a tone that we are ignorant, or under performing. From what you've written, it is clear you have experience with driving efficiently, and experimenting with different cars- but you may experience hostility with a more hostile tone. A lot of us, specifically mentioning me, want a mod that will pay for itself. My grille block isn't made of platinum, it's made of coroplast and weather sealant.
I don't mess with tuning because of my warranty. Others for other reasons. We all want to help get each other get better fuel economy, but we try to do that in a friendly environment, too.
And as much as I love Top Gear, over the years, they have done a lot of things that are either clearly scripted, or sabotage themselves. I take their performance as entertainment with cars, more than factual information.