Ok. The P0455 is "EVAP System Large Leak Detected". It's a very "general" code. First and foremost, double check that fuel cap. I know you said you replaced it however- you will need a cap that meets OE Specs. Those "universal" or "locking" fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. I just want to completely rule this out.
If you are 100% positive the cap is good, then there are a few different possibilities from here, unfortunately. This can be a faulty EVAP Purge Solenoid, Vent Solenoid, EVAP Canister or Fuel Tank Pressure Sensor. There ARE some tests that can be done to confirm where the problem lies, but it will require the use of a scan-tool (if you have a scan-tool, I can provide the flow-chart for you). However, if you are smelling fuel then I am leaning more towards this being a Faulty/Leaking Fuel Tank pressure sensor. It's mounted to the top of the Fuel Pump Assembly at the top of the Fuel Tank.
Again, I'm sorry I can't be more specific, but with such a general code, there would really need to be some testing done. But, like I say, based on the fuel vapor smell, and the knowledge that the FTP sensors on these vehicles are a common fail item- this is where I'd suggest starting. It's a good idea to inspect the vacuum lines to/from the Purge and Vent Valves for any cracks, holes or loose/missing connections as well. If the visual inspection checks ok, I'd say FTP Sensor.