Holy crap. Dude, I know it sounds very cliche but, you definately have a blown head gasket. When you said "the coolant resivour usally overflows on trips like this" that is a dead give away. I don't care if its 120 degrees out and you are redlining it, the overflow should never overflow unless you have combustion gases entering the radiator, period. You have the same symptoms that my car had but yours are alot more severe because you just keep driving it. All it took was for mine to overheat once and the overflow was overflowing and I got sick of it and tore the bitch down. Some days it will overheat and some days it won't right?
That pipe you used looks like a downpipe.
Nice stock air box
