I had an ask round and there is no real agreement on how to spray against peach leaf curl. The best, reasonably authorative article is given below:
Peach leaf curl is a fungal disease so I doubt spraying with an insecticide will work. I have found no o0bjections to spraying with bordeaux mix which is a fungicide.
What is strange is that some reputable companies offer quite expensive plastic and polythene barriers to prevent rain falling on the tree from January to May. This would indicate that there may not be a spray that works.
Another USA based article is given below. This where they grow peach trees in a huge way so they should know what they are talking about!