The rectangle cut out is facing the back of the passenger side lamp. It has to catch some outside air though any small gaps from fender and headlight and hood....anyway, I do feel a bit better throttle response...because I just don't get how the stock location could feed any air from the side and the air would have to take a right turn to go into the intake box....at least my mod, the cold air would come from the gaps....any thoughts...?
Think about it: The air finding it's way in between those small gap(s) in the front can not flow more/better/more smoothly than that relatively large hole in the side that's decently isolated from the engine bay. That air coming in through the front gets stalled trying to squeeze through those gaps so it's surely not any sort of "ram air" effect. Aside from the volume and speed aspect, that area is a hot spot because you have a huge forced-air heater right there in the front- the radiator. Next time you go for a drive, pop the hood and feel all around the front of your air box. It's not gonna be cool. Also, there is no "cold air" to be had except during the winter months.
The air coming in through the lower side of the fender is fed into and fills up that area inside the fender. So, it's already "there" and immediately gets sucked into the inlet side of the air box. It's not really having to make a 90° turn as if the flow is directly and exclusively going from the slots in the fender liner, up, and then making a hard turn into the air box. Sure, it's not a ram-air effect, but at least it's more of fresh air than the heated stagnant air coming through the front. Compare it to the cowl induction hood. The air may not be forced into forward-facing nostrils, but there's an area of high pressure air that builds at the base of the windshield that's readily inhaled as it's fed into the rearward-facing duct. A side note to the ram air effect, if you didn't already know, is that it has been proven to be ineffective at any speed your Tahoe will ever be capable of. As far as you feeling better throttle response- that's purely subjective without having actual testing and official numbers. Most anyone that does something, especially something permanent, to their car in hopes for better performance is gonna "feel" more power. I can see where there MAY actually be better off-idle throttle response since there's a huge hole providing more volume. This would be great for all those times you wanna race someone to 20 MPH. But, once the engine bay gets good and heated, any gains you may have from the extra volume are negated by the timing being retarded due to the higher intake air temps. For the other 99% of your driving, feeding your engine air that is isolated from the engine bay is best.
