Ok guess im a "newb" but ive owened my b5 12v since oct of last year. Ive brought the car back from the grave over this past year repairing/restoring it to new.... long story short. My heat was starting to lack so i flushed my core and to no surprise it was slighty clogged. I opened a can of worms so to speak..... it didn't fix the prob. I then did t-stat water pump timing belt roller and tensioner pully. Also replaced my hard collant pipe bc the coolant bleeder was stripped out. All said and done ive bleed the coolant system to DEATH and i only have luke warm heat under higher rpms. So i flushed and reflushed my core in both directions. And not with a garden hose i have the air/water combo tool to do it properly and bled and bled the system pressurized and unpressuriezed still no heat. So i moved inside the car all my actuators or motors... ie. Blend door motor and flaps. All function properly in both directions. So i moved to vaccum.. been needing to replace the lines any way... all replaced but one that i cannot fig out where it connects. The line runs under the heater core lines through the firewall and into the car but seems to disappeare. Where does it go? Cause i still have no heat... And what could i possibly have missed? SMH

Thanks in advance