Lambda sensor problem

[Andrew300]

Hi all , My Atom is running really odd ! At about 30 to 40 mph I can only explain it as on and off power , but with a bit of right foot the acceleration is really sharp then drag . I phoned the factory and spoke to Steve and he said it could be melted wires behind the number plate . I have checked them tonight , all are fine , I can only think it's the sensor . Any ideas ?