The system on my 1998 only holds 19 ounces of R134a; that is a factory weighed in charge.
With the suction line cold and the discharge line hot; I would recommend you connect gauges and see what the pressures are actually at.
You might be a little over charged if you added 20 ounces.
With the vehicle stationary, the condenser fan running and the engine idling; the suction should be around 40-45 psi and the discharge should be around 300-325 psi. This pressure will drop when the engine rpms are increased or when the vehicle is driven and air is pushed thru the condenser and radiator.
Those pressures should provide you around a 45* air temperature depending upon what the outside air temperature is.