92 corsica, coolant leak on driversw side under throttle body ?? anybody know of an adapter for a regular pressure test kit to fit the resivior?

The cheapest is to take the vent line for the water reservoir and remove the large rubber gasket from the tester and use a gas line clamp to attach it to the tester.
Numerous adapters are sold on ebay.

What engine?

It should work on any newer chevy with a coolant storage tank with a vent line. I use an adapter that threads onto the coolant tank. I put a bolt into the vent line with a hose clamp on a 1999 malibu 3.1.