Airtec is the best, in my opinion... You might think that the MST is the best bang for your buck, from the results... but, if you do any street driving, there will be heat soak on the MST. Park the car, go in to get a bite to eat, come back and out, and the area under the hood will be heatsoaked. Even just stopped in traffic. Because its not an enclosed sealed system, and the area that it uses is large, it will take some time to get it to clear out. Once it does, the power is there, unlike HKS.
You want an enclosed sealed system, so you don't ever suffer from heatsoak, and you want a very good flowing system. Therefore, bang for your buck, it's the Airtec. cheapest enclosed system that gives results (good flow), and doesn't heat soak.
The test showed which intake flows the best and which one reaches its coldest air, and stays there. You can derive this from the hp gains and temp readings, they show. Clearly for the money, Gruppe M and Sprint are huge failures, as is ITG, but you don't pay much for the ITG. So, I put ITG above Gruppe M and Sprint. These are midpack intakes.
I put the intake that will likely heatsoak, the MST, above the others, because it clearly flows well and is cheap. Airtec, Eventuri, and MST are the top intakes, in my opinion, but the Eventuri is for those that feel it's an investment that they will get back when they go to resell it.
Tegiwa never gave their preference for bang for your buck, here's what I would go with ($ amounts are in euros):
1. Airtec, 12.3hp gain for $600,.. best gain for $, no heatsoak
2. Eventuri, 14hp for $1248, ...... looks incredible, 1.7hp gain over best gain/$ intake, money is no object
3. MST, 12.2hp for $409, ........... best gain for $, but w/heatsoak
4. ITG, 7.1hp for $474,............... more gains than HKS!, but 2nd cheapest, no heatsoak Edit: version 2 gave 9hp
5. Sprint, 9hp for $1295, ............ gains are not best, but looks incredible, minus the blue coupler???
6. Gruppe M, 8.7hp for $1435,.... most expensive, gain is disappointing
7. stock, no gain, but it's free,...... since it came with the car, no heatsoak but not very good at drawing air, and needs a pickup tube modification/swap (which can be purchased)
8. HKS, 5.1hp gain for $936,....... if you just want noise, then this is your intake. As a bonus it gives 5hp
Edit: Their testing methods, and gains are questionable. There is a part 2 to their testing [which revealed testing issues], and on that day Eventuri made 7hp gain; and ITG fine tuned their design, created a Version 2, and made 9hp gain. So, does that mean ITG makes more hp than what we previously thought was making the most hp gain, Eventuri? Maybe ITG is the one to get... and 5hp gain can be subtracted from some of the part 1 tested intakes...???