My vokera is making whinning noises?

Had a problem with my vokera linea 28, first the heating would reach about 80C on the temp display then cut out, about two days after this happend the boiler started making quite loud whinning noises, had a gas man round and he has changed the direrter valve motor cleaned the heat exchanger and put in a new pump. The heat now does not cut out but the whinning noise is still there. anyboby got any ideas. One more thing the gas man took out 15-50 pump and put in a 15-60 pump is this ok.