My pump makes strange sounds as if it is running out of water to pump and glugging sounds from the system. I've found that if I turn down the speed of the pump to the lowest it doesn't seem to take in as much air to the rad's. If the rad's were not balanced would this make a difference. I've just had a new boiler and programer fitted but not pump rads or piping.
Any idea's please.

What is the water pressure? System may have a bad pressure reducing valve or simply need the air purged. Many pumps are water lubricated, if you continue to run the pump dry you may ruin it.