I put one in my 1997 T4R, it seemed worth it but to significantly be able to verify what the specific pluses and or minuses were or are would be next to impossible with my limited or should I say zero availability in test equipment.
The feature of being able to rinse out the filter after applying the solution to dislodge dust,bugs, and all other foreign impurities lodged in the paper mesh of the filter was kinda cool, it can sort of, over time pay for it's self from a TCO perspective.
Sounds nice too, the sound makes you feel like your going faster, and it may well be a psychological mind trick, as in YOU psyching yourself out, after all you did drop some significant cash on this addition so your expectancy of return is high, naturally.
Installation is TOO easy which makes made me wonder is something this easy to do really going to give me what I think it is?
Hope this helps.