My 201 has a 14.5 gallon tank. I'm not aware that the 16V version had one that was any larger. IIRC the 124 chassis is 18.5 gal.

About the time my reserve light comes on it will take about 12.5 gallons.

If your 16V is an '85 it is gray market, and the emission control system configuration is probably not documented.

How have you gotten it through emission tests?

Duke