Well, if you guys were interested in an estimate on how much of a difference intake air temperature can theoretically make it can be estimated with ideal gas laws. Since we always want about the same ratio of air to fuel we can focus on just the air and assume it's bringing proportional fuel and power. Say 70 outside temps and 120 under the hood, that's about 529 and 579 in Rankine. Gasses expand proportionally with temperature so density goes in the inverse of temperature. So 579-529=50, 50/579=8.6% decrease in volume or it's at 91.4% of what it was. Density = m/v, so 1/.914 = 1.094. So by dropping 50 F from 120 you should pick up 9.4% hp, not to mention you should have a cooler running engine and improved efficiency. Now if the intake tube is restricting flow this would of course offset the power gains, but I think that if you're moving air is actively being crammed into the intake tube, so I bet you're actually getting more flow with the tube than with a flipped lid once you're past 25 mph or so. If that's the case it might be in the ballpark of 15%.
Well this is all fine and dandy IIIIFFFF everything is ideal and in the real world, it is not. But even if were, 1.094x180=196-20%(drive train loss)= 157 whp. Stock @180= 144. You should feel 13 whp... but you wont as in theory is fine and dandy in theory but not application. Also even if 13 hp was added, who are you racing with 157 hp and 5000 lbs? That Honda will beat you, its half the weight. And 13 hp isnt going to give you 13 ft lbs of torque either.
And last note, if you have your egr hooked up... Its heating the intake air anyways. So you are loosing that cool air effect.
Here's what I did on my '79 K15 (small block). I got an '81 and up air cleaner lid & filter, which is 2" taller. IDK if it works with the '87 TBI or if it would be too tall. I purchased the cold air tube and cut the end off the diffuser at the core support. Creates a ram air set up.
Ram air is a methodological beast. In order for ram air to work, you have to be doing something like 100 mph. I forget the math on it, but we tested it on 4th gen F bodies and basically, it doesnt exist. Pulling in cooler air does help atomize the fuel better, but once again, if you have an egr valve connected, your heating the air up anyways. Also, the air box is metal, sitting on some old american iron, so once again, the air is being heated.
Still, that all said, Its better running the tube if you have it, but you wont notice the decrease in performance running an open filter.
We could get into advance thermodynamics and physics and blah blah blah, but simply put its not going to change things. Its great for very small changes and environments (not the environment, that's a different subject on a much larger scale.) But just remember basic chemistry and physics, heat moves into cooler spaces.
