No pegboard. No luan, either, unless the vinyl manufacturer specifies it. That is a quick way to lose your warranty, guaranteed. And, any installer that is willing to put down the wrong underlayment (at no time is pegboard suitable for anything but maybe stretch carpet, and even then it would be a stupid idea), and doesn't know what the manufacturer specs, shouldn't be allowed in your home. A warranty is a tangible thing, and hard enough as it is to maintain. No installer or builder should tell you what underlayment should be used; the maker of the vinyl/holder of the warranty holds that authority.