Ive read thru the threads and cant get much info this just started happening and is getting on my nerves bc i gotta go home b4 i pump gas n stick a snake (pluming tool) down the neck and release pressure/gas to fill up

car is a 99 m6 116k n i added ls6 valley/intake not to long ago n weeks b4 that i removed the evap under the hood n capped it off at the intake n near the fuel line beside drivers fender wheel and took out the silnoid

could it be a check valve or clogged up charcoal canister????

 

Yes, clogged charcoal cannister and/or clogged purge vent.