To the OP Stallen
There is a possibility that you are breathing CO. Since this could be a danger to you if we are correct I will be sending you a email from the site directing you to view this thread. This is a guess but an educated one and we are interested in your safety IF this is the issue at hand.
CO is a dangerous gas. Please make no bones about it. Please take precautions to protect yourself from continued inhalation of this gas.
Please click on this link http://hvac-talk.com/vbb/showthread.php?t=853762
I can see from your IP address what part of the country you are in. We have a Professional Member very close to you. Scroll down on the map to your location and call this Pro immediately.