OIl pump -head gasket

What is your question?

Had my head gasket replaced about 8 months ago, the day I took it from the shop, I had oil pressure problems, when the engine is cold the oil pressure is 45 - 55 lbs, when the engine is warm/hot, and I am at idle or at a stop, the oil pressure drops to 5 - 7 lbs, once I press on the gas the oil pressure goes back up. could they have done anything to cause this?