Every time my furnace kicks in the duct work right above the furnace thumps. Its the duct work expanding with the heat kicking in. I was told to drill a 1/2" hole in the side ducting of the heat side as it leaves the furnace to relieve some pressure. That didn't help. Any ideas how to stop this. I'm all ears. I have A/C also, so there is a A coil present. Yet my other houses had the same setups and no issues.