Guy:
I reviewed the data above.. The scope bandwidth reommended for ripple and extraneous noise measurement is not more than 20MHz . The scope in this data is detecting E field noise ( which is not actual present on the output bus.
PTH04T230W at 0.0A to 6Amp load is 13mV. The PTH04T230W requires a minimum of 100uF ceramic capacitance plus 150uF non ceramic capacitance.
PTH04T231W is the all ceramic version .
Any PI filter on the out put bus will directly affect transient response and possibly the stability of the power module. I recommend adding additional 47uf or 100uf ceramic capacitors on the output bus. the ceramic capacitor are the best reactive component for ripple attenuation at these frequencies.
Tom