CEL problem.. dealer wont fix ?
 

I had a car go into the dealer last week to get a X-mile tune-up and 1minute after driving off the lot a check engine light comes on! I call the dealer to ask to come back to have it looked at and they tell me they are busy and i have to come back another day. So first off that is a little screwy, but the car goes back later. Once we get the car back to the dealer they tell me that the light was on because the gas cap was not on right ! A- the light came on after they serviced the car and B- i filled up the car in between the time the light came on and it was taken back.. so in that time, if this was legitimate, I had put the gas cap back on the car and it was tight. So that does not make sense at all.
Anyway they clear the code and say it is ok now. A couple miles down the road.. CEL AGAIN ! So now i dont believe the dealer right now so i take it to Autozone and they gave me TWO codes that are flashing, which would make the dealer wrong since they said only one code was thrown. The two codes are P0455 and P1448, which say Evap Emissions.
So im sure there is something wrong with the emissions part but why would they tell me the gas cap was off, when it clearly wasn't the problem.. plus, what is the problem !?
Can anyone help me figure it out, i don't want to take it in again and they tell me that windshield wipers are old so that is the reason a CEL was thrown.

any help!?

evap emissions relate to the the fuel tank, and vapor recovery. One way to get a code for an evap leak is to not have the gas cap on tight.

Inside your front pass wheelwell, just about right behind the side marker light is an air pump that attemps to draw vacuum on the fuel tank, and charcoal canister, all that stuff linked to the vapor recovery that I mentioned. If it can't pump down to a certain level within a certain time, you get a code.

Your problem can be ANYWHERE between that pump, and the gas tank.
My code went from 'evap leak' to 'large evap leak'. Theres a good chance I have a leak in a line, but I also know my *Leak Detection Pump (one of a couple official-ish names I've read for that pump) has issues, maybe bad seals, and it sounds like theres midgets having sex on a squeeky mattress in my glovebox while its running.

There is a procedure to figure out which sections of the system the problem might be in, it involves removing a line from the pump and plugging it, and noting the pump frequency or something... cant remember exactly. Its in the Bentley, but my PC is down, so I can't pull it up for you.

Actually, if YOU find that procedure, let ME know, because I'm 4 months overdue on my inspection, and it'll eventually catch up with me, and I can't pass w/o fixing that evap problem.

I know of no way to pull the evap system like you could with the PCV stuff or SAI.