Here's the genuine ABF 16v article, this plug fills your empty distributor port after converting to Coil On Plug ignition, for example:
Also consider a cam trigger. This is the most accurate means to control ignition timing and fuel injection. USRT's famous VW 16v Bosch Trigger is a popular choice. Or, go with the even more capable VW 16v EVO Trigger.
Keep in mind that older ECUs can't process all the information that these cam units deliver. So, crank trigger your 16v with this "60-2" solution instead:
The MOST ELITE setups run both a crank and also cam trigger together. Regardless, that space is empty. Here's the factory way to plug it: