Lambda sensor

[Felizardo]

(1st, Sorry for my bad english from "google translator")

I'm desperate to get my car to work properly.
A mechanic made the normal maintenance in my car and replaced the gaskets by a new kit, and was never able to get it working perfectly again.
First he said it could only be the injectors. They were cleaned and continued the same.
- Injectors cleaned and inspected by specialized company
After several attempts the following has already been done:
- New spark cables
- New distributor rotor
- New distributor cap
- New distributor vacuum valve
- New sparks
- New canister filter
- New Fuel tank
- New Fuel pump and filter
- Distributor, valves, adjusted

The engine continues to fail when passing between 2000 and 3000 rpm.
Sometimes it fails and the rotation doesn't want to climb, but after climbing the car has strength.

After consulting the "Bradley Artigue" manual, I decided to take a look at the engine.

I started to check Lambda sensor and nothing. What I found is a screw plugging the hole as it is visible in the photo (the catalyst had already been removed from my car for many years). Is the lambda sensor not necessary? Should I put one new sensor again? Where is the wire connector, I can't find it?

[redcars]

The lambda sensor (O2 SENSOR ) is located in the exhast manifold on the top side. The wire is not far from the coil. Someone has added that bong on the exhast pipe, it didn't come from the factory like that. I have two with FI and have worked on 4 others and the O2 sensors where on the top of the exhast manifold. Best of luck.