My stock 93 LS failed today for 3 reasons. Fuel cap failure, broken evap canister, and ignition timing was off. I did pass the sniffer test though.

Ive already replaced the gas cap and evap canister with used/good ones from a junkyard. My timing was at 12 BTDC. The tech said I need to be at 16 degrees in order to pass. My question is if I set my timing to 16 degrees will it effect the sniffer numbers enough for it to fail? I think Im gonna let a shop deal with the timing cause I have no clue on how to do it.