I wonder what the cats will think about this?
The mixture goes quite rich at full throttle anyway, and they just temporarily stop working as effectively. During cruise, the closed loop control will bring the mixture back under control, so the "chip" won't affect mixture, unless it takes the fuel out of the adjustment limits allowed, in which case you'll get an EML.
The ECU might give you a little more ignition advance if it's fooled into thinking the air's colder, but as has been said, it'll be a minimal adjustment.
At the end of the day, VX have spent a lot of hours setting up the engine management, so the likelihood of improving it in this way is slim. Granted, there are probably some compromises in the factory setup to get the emissions right, and to guarantee that it doesn't grenade under the most arduous conditions, but the only way to get an improvement, and a small one at that, is a properly developed chip.
Kevin