There is no new technology...its the same p.r.o.m. that was installed in the ECM many yrs ago, just a slightly different program, thats all. Nothing new there. Even the so called "leap" in computer technology from TPI to Sequencial port Injection (more computing power) only yeilded a very few more HP and virtually no gain in MPG. The L98 gets about the same MPG as the LT as does the LS.
ALL these aftermarket chips/proms offer the same results on THIER test engines under THIER control, in THIER test enviroment, with THIER engineers and technicions instructed to deliver some results that the marketing dept requires in order to sell THIER product.
Sure, you can alter the fuel/timing curves on the chart at the expense of emissions and/or longivity. I'm certain that you can alter the program to get 30+ mpg at a given speed....under very specific conditions that you'll never see in the real world.
The only thing new here is the marketing strategy. Better gas milege than the avg in a Corvette is relative. Better than what? Better than it used to be>? doubtful. The engine size and induction system severly limits what can be done to stretch a gallon of gas. Increased performance? sure...at the cost of more fuel used.
At the mid to high 20s for hiway milege, thats pretty darn good for what these cars are. Its not going to get any better than that. Keep it tuned, keep your foot off the floor and thats about as good as it'll ever get.