slow starting

I hope somebody can help me out there. I have a 96 AWD that does a lot of sitting around, the car only has 51,000 miles on it. I can let the car sit for a day, week, or month and it starts up within one or two rotations of the engine. However, once it has warmed up and I shut it off and let it sit anywhere between one hour and eight hours it is harder to start. It always starts, but when it does it sputters a little, smells like fuel, and takes three to four seconds to start versus the instant start if it sits for a day or more and you can see the light blue smoke coming out of the exhaust when this happens. When it starts correctly there is no smoke and the car uses no oil. My local Subaru dealer wanted $300 to trouble shoot the problem because they think it's a fuel injector leaking down into the cylinder and causing it to flood but they couldn't guarantee it's an injector without putting all that labor in it first. Anyway, does it sound like an injector or do you think it could be a O2 sensor or engine map sensor? Anybody out there have a similar problem? I'm open to all suggestions. Keep in mind, I'm not a master mechanic that can get into complex diagnostic work. Thanks for the help.