[smash]

Rolling roads are good for only one thing - comparative tuning. The outright figures mean zilch.

You can get a decent increase in power reading simply by over inflating your tyres. Get your car on the rollers, get a baseline figure, adjust, check the figures again. Preferably same day, same conditions.

NA remapping, well, essentially all you can do to effect peak power is tweak the mixture and timing - you can't get any more air into the engine so it all comes down to AFR and how much you want to push timing.

Remember, manufacturers er on the side of caution in terms of AFR at WOT to allow for engine longevity - there's a tolerance - whether that's 10-15% is another argument....and also remember some manufacturers have been known to detune their own engines - my old Toyota 3ZFE lump being a case in point.

My brother works for Land Rover developing maps and carrying out hot and cold climate testing. I can tell you that they do look at after market solutions and test some of them. One I can remember was the last iteration of the classic mini when they were looking to get the magic 100bhp out of the Cooper S and were looking at aftermarket injection systems - they tested a Weber system and let's just say they couldn't recreate the manufacturers claims (by some way). In the end they came up with the MPi which was actually a clever way of dealing with the siamesing port issue