Guys need some help on this one.

I have a 2003 WRX wagon that recently started having over heating problems(note during all this the temp gauge has never made it to the full hot mark). It began a week ago leaving home and the temp gauge started to rise. We were close enough to get back home, but on the way back home it dropped back down to normal and stayed there. First thing I thought was there was air in the system. I did a couple of different versions of removing the air. The car would act normal while doing this at home, but within 10 min or so after taking it for a test drive it would take off again. I then went ahead and replaced the thermostat with one from Subaru. Burped the system multiple times during the day until it wouldn't take any additional coolant then take it for a drive and bam temp spiking and air blowing cold through the defroster. Spent the day yesterday draining the entire system again burping the system till it wouldn't take any more, let it sit overnight and levels were full this morning. Took it to the gas station and on the way back same thing temp gauge took off and cool air through the defroster. I have no oil in the coolant, no coolant in the oil, and have a combustion leak tester for the coolant that tested clear as well. The water pump is making no noise or leaks as well. My only other thoughts as it seems the only variable is boost is that the turbo could be injecting air into the system(if that is even possible). I'm about ready to call it quits and just sell it or part it out.

Mods to the car, but most of these have been on the car since early in it's life.
Catless up-pipe and down-pipe full exhaust
Cobb stage 2 tune
and a bunch of other stuff that would have no affect at all on the engine.

 

I'd get it checked. Despite not seeing coolant/oil mixture, based on what you've already done it still sounds like head gasket possibly.

 

So you are ready to get rid of your car before you even take it to a Subaru shop?

In your shoes I would take a drive to see one of our Bay Area shops (Mike at GST, Mert at RBMS, Paul at FW) and have them diagnose it. These shops have seen it all so I'm pretty confident they will get to the problem

 

I may, but just trying to see if there could be anything else. All the checks so far show no sign of head gasket.

No oil in water
No water in oil
No smoke out exhaust
No combustion gasses in coolant
No visible signs of leakage around heads

 

RBMS is where I'd probably go, but they are in Hayward.

Since you are in Santa Clara, there's also Mann Engineering. He can diagnose. https://www.mann-engineering.com/

AHQ is in Mountain View and the owner is/was an iClub member.

Some people had negative things to say about Garage One in SJ, but I had no issues with them.

 

I'll swing by Mann since it is between my work and home.

 

Well here is the update. I finally got around to working on the car due to my other projects. Pulled the engine and tore it down. While tearing it down found that the rear lower driver side head bolt was broken. This was the reason it was only occurring under boost and no physical external leakage.

Now I have the fun of extracting the broken bolt and building it back up. ARP studs should be here tomorow.