My 2-cents on the gas smell
Ok- I just bought a 2005 Colorado about 6 months ago as a vehicle to drive to work, and to haul around a few things. Its a CrewCab with 110,000k miles. I've replaced the headlamps, front grill clips, and window actuator so far. Once it got cold here, I would start up the truck and it would reek of gasoline. I thought maybe it was just really bad smelling exhaust, but I would hop inside and it reeked of gas also. After dealing with this for a couple of weeks, I decided to try and track it down. I think my solution was 1 of 3 things I did. 1- I took off my throttle body to clean it, as I had a CEL and rough idle. The cleaning eliminated the CEL and rough idle, but I also noticed the air duct hose connecting to the throttle body itself was folded back on the bottom side (hard to see or get to). When I put everything back I made sure this was fully onto the inlet of the throttle body and the hose clamp was tight. 2- I noticed when taking the resonator box off, that the small crankcase ventilation hose towards the back (underneath) was really dry rotted and cracked. I ordered a new one off of EBay and replaced it. 3- and probably least likely - I noticed the small hose going to the top of the fuel regulator was not all the way down. I noticed this while looking for leaks aroung the fuel pressure regulator as some others have suggested. Anyway one of these 3 changes seems to have fixed my gasoline smell for good. We've had plenty of cold days where I have ran the heat, and nothing! Keeping my fingers crossed that this fixed it and hope that it may help someone else out. My theory is that it was either the crankcase hose or air duct to the throttle body, letting gas\exhaust smell fill up the engine compartment and then the vents sucking it right into the cab. They are all in close proximity, so it makes sense to me, anyway!