EVAP Code P0446

[J]

I truly hate issues like this. I have a Continuous Memory Code on my Evergreen car. I just need a direction. The car still has a miss on the #6 cylinder that is related to a damaged piston/valve (just did a leak down test and it won't hold pressure at all).

Here is what my AllData says:

HX18 - DTC P0446 OR P1450: Check For Visual Causes Of Excessive Fuel Tank Vacuum

Continuous Memory Diagnostic Trouble Code (DTC) P0446 or P1450 indicates that Self-Test has detected the Evaporative Emission Control System has excessive fuel tank vacuum. Also, a DTC P0446 indicates a vent control malfunction. Possible causes:
EVAP canister purge outlet tube (EVAP canister purge valve to EVAP canister) blockages or kinks.
EVAP canister tube (fuel tank to EVAP canister) blockages or kinks.
Fuel vapor elbow on EVAP canister contaminated.
Restricted EVAP canister.
Canister vent (CV) solenoid stuck closed (partially or fully).
Plugged or contaminated CV solenoid filter.
EVAP canister purge valve stuck open.
Fuel filler cap stuck closed (no vacuum relief).
VREF circuit open in fuel tank pressure (FTP) sensor.
Damaged FTP sensor.

Which direction would you guys go? Keep in mind I have no testers and I already snagged a used gas cap from a Taurus at the junk yard.