Don't waste your money on closed loop, I have this facility on my ecu, but don't use it, if it is mapped correctly then the gain will be zero, if you were running a cat then that is a different matter.
I was getting 40+ mpg on a run as I call it, but that wasn't motorway or anything involved going through the centre of a major city and only about 10 miles of motorway at a steady speed.
CL is way over hyped imo, it's a simple flick of a switch to use mine, I never bother, bit like the massively over hyped coilpack, if there are no issues with misfires under boost etc caused by the old fashioned ignition then there is no "gain" to be had.
Beware of greens they can vary a lot, my last set of dark greens 0 280 150 803's were at 80% duty at around 300 bhp, on the std rail pressure 3.5 bar, these had just been cleaned so were the lowest cc/min you should get, used ones are a bit higher.
A live map IF done on the rollers would get the best, as this way any combo of speed/load can be held, unlike road mapping, I would not bother with road mapping personally.
Just my opinions.
tabetha