Using MOD16A2 in GEE to extract best quality of PET

Question

I am beginner with Google Earth Engine programming. I want to know how I can use MOD16A2 to extract good quality values of potential evapotranspiration data (MOD16A2)? because I extract the PET of MOD16A2 and I compared with PET calculated by FAO56 PM, I find the bug difference between this parameters. My study area is agricultural area.

This is my code :

//Load the dataset
var dataset = ee.ImageCollection("MODIS/006/MOD16A2")
               .filter(ee.Filter.calendarRange(2001,2020, 'year'))
               .filterBounds(aoi);// aoi= study area

var PET = dataset.map(function(img){
  var PETmm = img.select('PET')
                 .multiply(0.1);
  return PETmm;
});
print('8day potentiel evapotranspiration in image collection',PET);
print(PET.size());
print(aoi.size());
print(PET.toBands());
// reduce the ImageCollection to singleimage with  multiple band
function imageCollectionToBands(imageCollection) {

  // put all images in 1 image with multiple bband
  var img = imageCollection.toBands();
  
  // Rename bandnames
  var names = img.bandNames();
  var newNames = names.map(function(name){
    var ind = names.indexOf(name);
    return ee.String(names.get(ind)).slice(0,10);
  });
  return img.rename(newNames);   
}

var imagePet= imageCollectionToBands(PET)
                   .where(imageCollectionToBands(PET).gt(100),ee.Image.constant(0));
print('8day PET', imagePet);
var marocPet = imagePet
  .reduceRegions({
    collection: aoi.select(['Nom_Locali']), 
    reducer: ee.Reducer.mean(),
    scale: 1000
  });

print('Feature collection of PET', marocPet);
// Save Value in google_drive  
Export.table.toDrive({
  collection: marocPet.select(['.*'],null,false),   
  description: 'PETStations', 
  fileNamePrefix: 'PET_Stations', 
  folder : "GoogleEarthEngine Data",
  fileFormat: 'CSV'
});