On the fuel dizzy there is a hole where you use a long 3 or 4mm(i forget, it's been awhile) allen key to manually change the fuel mixture. Usually you adjust by 1/4 turn increments. It's helpful if you know exactly what mixture you're running so you don't over do it.

if needed i can go take a look at the tool for the sears part number. It does have to an abnormally long one.

As far as switching management for proper EFI... Digi1 is a better bet from a corrado than digi2 from a regular golf/jetta. Last I checked on ebay you can get a full fuel rail/FPR/injectors/ecu/harness for under or at $300. I remember a couple places burning chips for digi1-16v's too.