This is 'eye candy' - bottom line. I like eye candy - it does 'nada' for performance, and very little, if any for sound especially if married with the f-sport exhaust. VERY few intakes deliver the performance values stated. The ones that do 'usually' are set-up with a exhaust that breathes better (ideally headers), a cam modification and a tune. All these are limited on the IS. The ECM needs to know what to do with the increased volume of air for more power - add more fuel, this usually come with a 'tune'.
No ones 'butt dyno' can pick up on 4-8 hp - it becomes a mental satisfaction. No bashing here meant - but trying to be realistic.
As for the lower part of the air box - the factory one stays and it is already plumbed to grab air from the area on top of the radiator shroud - so nothing changes.
The intake is a nice accessory with the 'Lexus fit / finish you expect - buy it because it looks good, not because you think you are going to get more horsepower...
Last edited by afdavey; 08-09-14 at 05:47 PM.