It would help if you could record the sound at put it on youtube or something. It doesn't sounds like anything I'm familiar with, but maybe I don't understand your description.
The heat soak may not make a giant difference, but why ignore it? Metal will clearly allow heat to transfer to the intake charge at a faster rate than plastic will allow.
I do agree that at N/A power levels, a CAI isn't helping, plastic or metal.
Anyone who uses the word "aint" in a so-called scientific study loses all credibility in my book. Exactly how is this test supposed to test the oil in any way that even remotely resembles the actual environment that the oil sees? Who operates their car at room temperature?
Read this thread...
That's only becasue they are sold with the oil plugs installed. The plugs can be moved from the back to the front to make a LH a RH or a RH a LH. Take a look at some heads the next time you get a chance and you wont find a difference except for the plugs.
Heads can go on either side if you move the oil plugs. The guides may or may not be interchangeable; I cant remember. If it says RH or LH, then they are obviously not interchangeable.
You probably have a leak in the crossover on the thermostat side. The new crossovers are aluminum and don't develop the fatigue cracks that the plastic ones do. Get a PI intake with the aluminum crossover. You will gain HP and no more leaks. Fix it soon or you will be stranded as that fatigue...