You need a proper air inlet temp gauge, Those readings from a scangauge via OBDII is way out.

A OBD scangauge can only be accurate if they are calibrated to each particular sensor. Universal ones cant do this.

I guess the offical Daihatsu OBD diagnostic tool, where you can select each exact car/engine on the menu should be reasonably accurate (you would hope).

Air inlet temp when boosting with a good intercooler would be around 40-50c measured after intercooler.

Inlet air temp air filter side is mostly irrelevant on a turbo car (unless extreme such as filter very close to turbo or exhaust),

You just need a large enough supply of well filtered air (decent filter size and quality).

If the ambient temp going into air filter is 5c or 20c, the boosted air when compressed and heated coming out of the turbo is still going to be very similar. Getting the air temp down as it passes through intercooler is the part to concentrate on. (ie bigger intercooler, Front mounted, Water injection)

Remember that lower (on boost) air temp gives you more power in 2 ways, more oxygen is the obvious one, But also less chance of engine knock (detonation) so the ECU is less likely needs to retard the ignition timing.

That's the main reason why turbo cars feel so much more lively on cold days than in the summer, The intercooler is working better, And less chance of detonation so the ECU is not retarding the timing as much.

Some turbo cars when put onto a dyno rolling road, will really suffer after only 1 or 2 power runs (power drops off)...there is just no way near enough cool air passing through the intercooler core compared to driving down the road. I suspect the YRV would suffer like this with the small top mount.