Gurgling and clanging sound coming from peerless gas boiler, how do I eliminate it?

Probably air in the water pipes. Find the nearest spigot valve coming out of the top of the boiler and open it, ready to shut it as soon as water squirts out, and stand so hot water doesn't hit you. Go upstairs and vent any relief valves on radiators or baseboards. If on a loop, you might get away with just the highest one.