It was an aftermarket heater core through ASG. where the heater core pipes come out from the heater core it has two pipes obviously. those two pipes have been "joined" from the two pipes coming in from the firewall through pipe joiners.

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2002 WRX (GDA) BUGEYE, 204BHP at 290Nm, daily driven

--MODS--
--> Walbro 255LPH fuel pump
--> Grimmspeed 3 port EBCS
--> 3" turbo back exhaust
--> Catless up pipe