Boiler problem

I have an Ideal Elan 2 boiler and for the past few weeks it has been making kettling noises and a sort of whistling noise.
Drained the system this weekend and fitted a new pump,also added sentinel x200 noise reducer, but the noise is still there although its a little quieter,does it take time for the noise reducer to get round the system?
Also you can also hear the noise in the upstairs rads.
Any ideas on what to do next?
I forgot to say it, i dont think the boiler is overheating as i have put a digital thermometer on to the flow pipes and the readings are not above the temperatures quoted in the manual.
Any help would be most welcome.

kettling and boiler noise is associated with air or poor circulation, check the boiler connections for scale.

Is the by-pass adjusted.

And what size pipes have you from the boiler and to the rads