In short better throttle response, cooler IAT's and increase in hp/tq.
The spacer adds volume and slightly cooler air entering the head. It also, provides increased cylinder filling at lower RPM, smooths out throttle response, helps to build boost quicker and lengthens the wave pulse of the intake charge.
I'll be adding a bored throttle body and spacer once received, along with the intake manifold spacer when it's available. Every little bit helps along the journey.
I'll make sure to post everything once it's completed. I'm in no hurry and making comparisons as I go. I'm not looking for peak hp output. Just solid usable hp, with reliability always in mind.
With some intake manifold tuning, I believe this will assist the little turbo to breath much better. Taking little steps with the intake first. More efficient air in, more power out.

I'm looking for everything to work well together, instead of just bolting a lot of parts on and hoping.
If can just find someone to make a bespoke; tube, equal length, intake and exhaust manifold. I'm still searching right now.
Thank you for asking. You have a PM!