Yes I know driving slower works. I said that early on and everyone hung me for that. Told me to drive hard during brake in. Which I was told by top engine builders that that is not the correct way to break in an engine but that is not the topic here.The oldest trick in the book works on old and new TDIs - drive slower.
You do understand that when coasting in N, the engine is idling (using fuel) so rpm are around 850 ish no matter what the speed of your car is and when coasting in gear, the rpm of the engine depends on the speed you are going when removing your foot from the go pedal and the gear you are in.
Thus, coasting in gear is not limited to 1000-1500 rpm above coasting in N and does not use fuel as long as the car is moving slightly above "idle rpm" (the ECM completely stops injecting fuel when coasting in gear above idle rpm).
So I change my driving to what people recommended for break in. No fuel numbers but just things I notice. I drive the car 22 miles to work and 22 miles home. I go about 3 or 4 miles through a town where it is 4 lanes and 35mph. I know people who have gotten pulled for going 37mph. So you go 35 not any faster. Then spend 5-10mins in line at the gate. Once I get on site it is 10 miles of 55mph. Some nice hills that are not too steep but steep enough to keep your speed constant. I was doing it in neutral then yall said don't do that so now doing it in gear. What I noticed is with my driving the rpms are around 1000 rpms different from in gear compared to N. I understand it depends on when you come off the pedal when in gear. I was referring to my driving. I also noticed that you coast a good bit further when in N compared to when in D. Some say if you do it correctly there is no damage to the DSG. Some say it will explode the first time you do it.
I guess my post in the beginning was meant for mods to the car once it is broken in. I read the post about down pipes, tunes, bigger turbos, and so on for gas mileage on the old models was wondering if any worked for the new cars. Don't care as much about power just wondering if any of these will add mpg.
Again thanks everyone for discussing these things with me to help me learn.