If no check engine light and no visual signs I would dye the fuel and use a ultraviolet light to track the leak down.
ACDelco 1148963 GM Original Equipment 10-5045 Multi-Purpose Fluorescent Leak Detection Dye - 1 oz
I would not associate a slow fill condition with a continuous gas Oder smell. One easy check I would do first is remove the evap vent tubes at the purge valve on the intake and check for BB's, BB's are small round charcoal pellets that look like a black BB. I would also check at the vent valve under the truck. If the charcoal canister ruptured the fight will be on its a difficult expensive job to cleanse the system of those BB's.
If you smell fuel you have a leak its not always easy to locate.
Google this
#14858: PRODUCT EMISSION
This TSB may come closer to your complaint.
#15-NA-019: FUEL ODOR
https://static.nhtsa.gov/odi/tsbs/2015/SB-10074727-7690.pdf
DEFINITION: During the fueling process a continual, occasional, or no-fuel nozzle shut-off condition has occurred.
Difficult to fill
Fuel fill limiter vent valve stuck closed
Evaporative emission (EVAP) canister restricted
EVAP vent valve stuck closed
Hose between canister and canister vent solenoid twisted or kinked if applicable
High fuel temperature
Fuel filler hose is kinked
Faulty dispensing nozzle
Ignition switch ON, vent valve closed
Over fill
Fill limiter vent valve stuck open or leaking
Fuel inlet check valve stuck open
Pre-mature shut-off of the fuel dispensing nozzle occurs immediately after engaging dispensing nozzle, tank empty
Restricted vapor lines or fuel fill pipe
High fuel temperature
Inlet check valve at tank stuck closed, fill pipe full of fuel
Fuel tank full, gauge not accurate
Pre-mature shut-off of the fuel dispensing nozzle, more than 1/8 of tank capacity dispensed
Kinked, pinched or plugged lines in fuel tank vent system
EVAP vent valve stuck closed or restricted
EVAP canister restricted
Fuel limiting vent valve stuck closed or obstruction at top of fuel tank
Fuel Spitback
Restricted EVAP canister
High fuel temperature
Ignition switch ON, EVAP vent valve closed