MRT have been very responsive to my questions via email so I'll copy and paste some relevant extracts:
Re: Hub dyno vs. flywheel #'s
Technically the dyno can’t measure power or torque at the flywheel (the only way to accurately do this is to remove the engine from the car, remove accessories such as air con and alternator and bolt it to an engine dyno – this is the figure manufacturers release as an engines “power output”). Our hub dyno measures the direct torque output at each wheel after it travels through engine, through gearbox, through all of the diffs and out to the hubs so there are some drivetrain losses between the factory quoted figure and actual measured figure as a result.
If you are trying to work out a reasonably close “flywheel figure” to compare against factory, look at what you’ve got now (240kw from memory) and add to that the difference between the factory quoted figure and the standard base figure (which is about 175-180kw on that car). So in other words if Mitsubishi quote 217kw as standard ouput and car on dyno has about 180kw, you’re losing about 37kw through the drivetrain in terms of friction, heat, drag, etc. If your car now has 240kw, the drivetrain losses may have increased nominally (ie a handful of kw additional loss) through some additional friction and heat but 240 + 37 gives you a new guesstimated output of just under 277kw at flywheel.
The power output value is actually a calculated figure derived from the measured torque outputs, so both power and torque presented on chart are comparable (ie they are measured and calculated the same way, so both are flywheel less drivetrain losses to give actual measured output at hubs as per above).
And when I asked if I needed to get an AFR gauge:
Not a silly question at all – but I’ll reply to your question with another question. If you had one, would you know what you were looking at and what it meant? My guess is that it would just be a random “thingy” to look at and mean very little to you in the big scheme of things. The raw numbers jump everywhere depending on what you are doing with the car and unless you know specifically what it all means and how it all interrelates with other engine parameters, it will be meaningless. J
If you want actual numbers - mixtures are around 12.0-12.2:1 at full load and high boost, a little leaner at lower load areas. They were checked and mapped on dyno, and are similar to the mixtures I run on both Brett’s track car and the other track cars we tune and look after, so you should be fine.
I really do appreciate the tuner (Ben) getting back to me with this information and I guess that's why they can offer a premium service at a premium price.