MDS, VVT, and transmission options?

I've heard MDS isn't really as big of a benefit as you'd think it might be. Typically only good for 2-3 mpg from what I've read, but different setups can always produce different results. That is roughly 10% improvement, so it's not small, but for shutting off half the fuel you'd think you'd get more.

My setup with just an overdrive transmission (T56 6 speed manual in my case) is creeping up on the 20 mpg mark. I know I have read about others on here getting into the 20s even without overdrive. A lot of it has to do with just tuning, though I don't know how much of that you can change with a factory computer. I have a wideband O2 sensor and aftermarket EFI setup, so I can tune however I like.