Renault Megane Bj.99 unround idle

Hello, our Renault 1.6 55 KW/75 hp has been running idle for months, or swallowing itself.During the ride you notice almost nothing, every now and then the speed at the traffic light times up to 1500 or 2000 u/min high after giving short gas it is gone. So far made to fix errors, Idle controller replaced, Exhaust sealed,Lambda probe replaced,Temperature transmitters exchanged power supply tested 5 V da.. OT-Geber measured thus 255 Ohm in tolerance. new, air filter new, vacuum hose suction tube sensor replaced. Visual inspection of all vacuum hoses. Now yesterday I decided to unscrew the heat sheet from the cracker and look in there, and I also found it. 2 cracks ! Think that it will be why it’s so shitty running in idle, or what do you mean ???