First things first.

Test the pressure. You will have two pressure readings. They must both be within specs.

It's been a while since I had the CIS system but the FIRST thing you have to do is get the pressure correct. A new pump doesn't mean anything if the fuel distributor isn't regulating the fuel properly.

If the fuel pressure is correct then check the engine for chain stretch/chain guide wear.

Pressure good and chain okay? Pull the injectors and check for spray patterns and flow. (I jump the relay in the fuse box to over ride the automatic fuel pump shut off, use a starter button to control the power) I use a baby food jar for each injector which allows me to compare the amount emitted.

The O2 sensor has very little to do with anything on the car. Don't believe me? You can completely disconnect the "computer" in the right side foot well (not the stupid "alarm" one but the one behind the kick panel) and the car will run the same.