GSL-SE block with S4 intake modified to fit did TB mod and so coolant just skips going through there and goes straight to the block

Alright I have replaced the radiator all the hoses the thermostat and the rad cap and I am still losing coolant... rather rapidly... Already checked under the intake... and its really starting to **** me off as its been going on for about 4 months now and a full radiator will last em about a week before its so low I'm in danger of overheating... the weird thing is I have no bubbles, no oil in the coolant, no white smoke, and it will drain just as fast if I don't run the car but I can't find any drip or anything where the car has been parked... I swear to god someone is sneaking into my garage at night and siphoning some out or something... anyone else ever experienced battle with the rotary coolant ninja and won?!?

 

Check the heater core.

 

Damn... I knew I was forgetting something obvious... what specifically should I look for though I'm looking at it but I'm not sure what a leak would look like unless it was gushing out at me... I mean I have no rusty runs or anything obvious... there is a valve at the heater core though right? could that be leaking? if so where is that located I checked the FSM but it was kinda vague about the location of a valve...

 

Under the passenger carpet. See if it is wet or not.