Sounds to me like you could have a clogged fuel line. That is if the fuel pump does turn on when you turn the key, if not you might note have power going back to the fuel pump. I would check the voltage on them then go from there.
Check the crank sensor
Chevrolet has not changed the injectors in the 3.6 L V6 motor since 2009.
I just had my oil changed in my 95 Supreme yesterday. They said it took about 4.1 - 4.2 litres. That would translate to about 4 - 5 quarts.
there are 2 fuel pumps on the car one at the tank and one in the engine compartment
you have bad orings, wrong size, orings or you broke the other injectors or the their orings
General Motors changed their passenger cars in 1992 or 1993 so you can be pretty sure that it is R134a. My 1995 CS uses R134a.
The 2.8, 3.1 and 3.4 are all the same block throughout all years. The only thing that really changed was the style of head, the intake, and a roller camshaft. It should be a direct swap for what you are wanting to do however.
On the front of the engine under the two ignition coils, follow the plug wires and under the coils is the ignition module. Changed mine twice . Works better now.
Are you getting power to the system?
the whole motor.
If the air conditioning unit in question has not been retrofitted or changed, it should take R12 Freon. However, if it has been replaced or upgraded, it may take R134A.
Was it missing and sputtering before you changed them? If no, then you could have got the firing order mixed on the distributor. Maybe if you didn't replace the wires also one became more damaged while removing it. If yes, maybe its your fuel, or injectors, and you need to add a bottle of cleaner to your gas tank.