Sadly I have the same thing happening. I have a stock 04 WRX. The symptoms are literally the same. The only thing that I would like to add to this is that when it is cooler outside (70 and below) there is no problem. But get above that mark and it sucks. I have been reading this forum and others for about a year and tried to find answers to this problem. Keep in mind I have zero experience with working on cars.
I went and got my airfilter changed, my MAF cleaned and checked and my IACV, and PCV checked and or replaced. I did these things from suggestions I heard either here or NASIOC, which I am totally grateful for. Now I have had no luck fixing the problem with all of these tries. I do barely remember a poster on either here or NASIOC say that the cruise control cable gets overheated and makes the engine rev high? I think that is what it said and I can't find the thread after searching briefly.
I do have an appointment with (MACH V/fastwrx.com) on Monday the 21st and will update asap. When I talked to them at MACH V they said that it was a bit unusual that a stock car would do that. Well any help before then would be appreciated.
Java, like I said I have no car experience but so far I have been told the stock intake/ air filter etc... are fine an functioning properly, and since our symptoms are the EXACT same I would say its not your intake. If that means anything. I know it gets pretty hot up in NY and it gets that way in NOVA too, so maybe the common issue is heat?