OK, I physically checked my Stihl 32cc 4-mix 4 stroke engine. indeed, the factory pulse barb is at the crankcase. But again, I want to stress this engine has some special porting going on that I need to research further that might make a direct analogy to your Saito/OS conversion invalid. My Saito conversions all went to the intake for pulse pickup. The problem (if it is a problem) is the WT456 from 4 stoke use had a spring that helped the pump diaphragm return. The reason, I believe, is the pulse profile from an intake source goes negative fine, but lacks the positive pulse leaving the diaphragm somewhere between. Hence, the spring. If I were you, I'd just try it.