This morning while taking my wife to work, heat on full blast, a really rich smell of fuel came through the HVAC vents. At first I thought it might be from the gas station I was next to, or the beater to the left of me... I turned the vent off just for the heck of it, and continued driving. About two minutes later, I turned the vent back on to find that the smell was coming from the vents again.

What the heck can cause the smell? I DO NOT smell anything from under the hood, and as far as I can tell, it isn't happening anymore. I ran the heat on full blast today on my way to work this evening, and didn't smell it through the vents.

About a month ago, the engine was replaced... (donor was my 1997 Monte LS 3100). Completely rebuilt, top and bottom, new Intake and exhast manifolds as well as all other gaskets...

Thanks,
StreetChariot