Well,
there's no odor even the slightest inside the cabin that would indicate the coolant leak. however possbile. But as indicated by some other posts there's no sign of a film buildup on the windscreen either. I double checked.
the heat that I kept the car on was at 70 to 75 just when the flaps flip and the heater kicked in. nothing too high at all.
as for the exhaust coming in, are we suggesting that the ventilation is proper when the temp is set at cold and as soon as the temp control is set to high, the heater kicks in the ventilation becomes all tangled up letting the exhaust fumes from the trunk inside the cabin somehow ?
THe reason I'm stuck with doing this myself is because the dealer is dumbfounded. their only suggestion was they want to throw a 1500 bill towards me to fix the vacuum actuators first and then look at something else. which is ridiculous because after fixing all that if they say they have to tackle the heater core they'll charge me for another 18 hours of labor to open the whole damn dash again. And i'm not ready to spend another 4K on a car that i've already spent almost 7K on. and at the end the car's resale value will never exceed 5500 to begin with.

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.