I ahve a 05 Impala w/3400 v6 When I start the car I get a gas smell. I don't see any leaks,, have replaced the fuel filter and the vacume hose to the PVC vacume regulator. Could it be the fuel pressure regulaort or a leaky o-ring on an ejector?

 

hmmm
where do you live?
ive recently seen alot of post on a trailblazer forum. and mostly vehicles about 3-5 yrs old.
where they are getting gas smell.
turns out that most of these guys live in areas where the roads are salted for ice.
the salt has corroded the area where the fuel pump attaches to the tank, and it leaks.
most report no gas on the ground- but can smell it.

is the smell inside the car too?
if it is....
have you recently had a stereo installed, stereo/amplifier combo installed?
My brother had an amplifier installed in his saturn some years back.
soon after that he started getting a smell of gas inside and outside,
turns out the installers used some big screws to hold down the amp............and drilled right into the tank
when the tank was full, it would smell strongly.... since the fuel was leaking thru there.
amp was installed in the trunk. but because of the fuel tank design..........

 

It happened to me once in a while. It was my fuel preesure regulator leaking slightly on start-ups. Cost about $60 at Autozone. Not too har to change.