I've read this entire "problem" (Marshalls) with interest. I am not a mapper but after getting the power from my old TDI I have a pretty decent (not amazing) understanding of TDI tuning. All I will say is this ... what a farse.
From reading the posts I see nothing wrong with PDTs position on anything, they seem to have actually gone out of their way to help!
MPG can vary so much from many things..
Wind speed
Wind direction
Small inclines or declines in the road
Tyre pressures (have you even checked this?)
Car alignment (tracking)
EGR contamination
Rate of DPF regeneration if you still have it
Quality of fuel (regular or premium)
Humidity effecting combusion efficiency
Hot weather causing heatsoak thus making the charge air less dense, decreasing power and needing more throttle to maintain a given speed
Air filter being dirty
Fuel filter being dirty
Boost leak (which has been tested I presume).
A remap in itself will not cause any noticable difference in engine noise. Outside of changing fuelling amounts at idle, SOI and injector duration, idle speed and EGR duty cycle, and only very slight. I had 5 different remaps on my old car and never noticed any difference in engine noise in any of them.
If you noticed the noise immediately you should have taken it back immediately. Not 3 months later. After 3 months after I mapped your car, if you came back to me saying "it's making a noise" I would say "okay I will investigate at a rate of £xx ph."
You are complaining over a 3mpg difference which can easily be caused by any of the above. Resetting the battery in itself would not cause a noticable difference in MPG. It would reset certain parameters as PDT have mentioned already.
I can drive the same route between where I live and a friends house and driving in a similar fashion, get anywhere from 33mpg to 42mpg.
You can look for a problem if you want but it doesn't necessarily mean there is one.
Fit a boost gauge which can allow you to see how hard the engine is working. You will be able to tell when you are driving up hill or down hill, or have the wind on your side or not. Then you can tally that up with expected MPG (not forgetting that with a battery reset the onboard MPG readout will be slightly wrong anyway and takes up to 1000 miles to re-calibrate).
Are you noticing less miles per tank or simply a lower MPG readout on the gauge? Because actual and displayed can be amazingly different...
It's a private issue between customer and mapping company but since it's posted publically (not sure what that achieves anyway) then it's open for opinion.