Idling Problem

206 1.6 XT 16v 2001 model petrol + lpg automatic car, I have a problem like this, guys.

Recently I went to the exhauster to have the exhaust tip installed, while he was showing him, your catalyst said that you need to remove coal. Anyway he took it off and replaced the front exhaust muffler. After 2 days, the problem of idling in the car and stopping started, when I first started the car, the hand of the hand slightly rises and goes down without pressing the gas, it finds its own setting after doing this 3-4 times. Meanwhile, the sound of a gas throttle in the car and the lights of the headlights and digital display seem to blink slightly. When I start driving the car stops slowly if I go. I went to the master, said, let's replace the spark plugs. We replaced the 4 spark plugs and the problem is still the same. He said, let's look at the feast return again in detail. Thanks.