Where is the low pressure AC port on a 1991 Camaro with 305 TPI engine Is it small line or attached to canister?

On a 1991 Camaro with a 305 TPI engine, the low-pressure AC port is a smaller diameter line and it's not directly attached to a canister. You'll find it on the drier/accumulator. The drier/accumulator is usually located near the firewall, on the passenger side of the engine compartment. Look for two ports on the drier; the smaller one is the low-pressure port. It's usually capped off with a Schrader valve.