Without seeing the images, my guess is that the noise is normal. The engine bay is an electrically noisy environment, within wiring looms there are wires with small signals (such as lambda) running next to other wires with high voltage spikes (injectors / ignition etc). To keep costs down there is no electrical screening in a wiring loom so crosstalk occurs (ie one wire picks up some signal from another).
As our test leads are properly screened from end to end it is unlikely that the leads are picking up noise so its probable that what you are seeing on the screen is actually whats happening in the wire.
Inside the ECU each input signal is filtered to remove such noise, fortunately PicoScope allows you to add filters so you can also remove such noise - the drop down arrow symbols next to each channel brings up the controls for this. For the lambda try a filter of about 100Hz to start.
Many people like to see both the filtered and unfiltered versions of a signal. So dont be afraid to add / remove the filter or change its value. The unfiltered version allows you to see whats really happening and check for drop outs & intermittent shorts etc. The filtered view is closer to what the ECU will see.