I noticed something the other day.... It suddenly got cold out! So I pull on the knob for heat and I get.... A face full of nice, warm exhaust fumes! Oh no. I thought I had a little talk with Comrade Trabi about this homicidal behavior last year and 38,000 kilometers ago. When I installed this "budget" heat exchanger I noticed an immediate increase in exhaust noise which I attributed to the thin metal of the heat exchanger acting like a speaker for the exhaust pulses. This is especially noticeable inside the car with the heat on. So a little preliminary checking revealed that yes, the fumes were emanating from the heat exchanger. So, out of the car with it and on goes the smoke machine for finding small leaks. It's leaking at small, barely visible cracks at the inlet and outlet. So, I cut the outer housing for warmed air near the inlet and outlet and folded it back. The outlet cracks were easy to weld up but not the ones by the inlet. So I came up with an interim fix until I can get a "premium" Vorschälldamfer. I merely cut away the outer housing so that the cracked area will not leak into the warmed air, leaking into the underhood area instead. A little creative bending, welding and a bunch of exhaust sealer to keep any leaks out of the cabin air and back into the car it goes. And... all the way home, nice fresh hot air with no nasty headaches, passing out or dying from CO poisoning! So... why would a relatively new heat exchanger do this? Well, the the thin metal prone to vibrating apparently fatigued and cracked. It's also possible that I had the manifold-to-heat exchanger bolts too tight. This could cause either more motor vibration to hit the exchanger or the weight of the exchanger to cause the inlet side cracks. Perhaps a little "give" at this joint would reduce stress on the exchanger, so I'm probably not going to tighten the new one quite so much.