Well, most pump products normally work on blood vessel dilation. Once the endothelial tissue relaxes, it expands, which allows for a higher volume of flow, which drops allows for blood to flow to muscles - but the action itself inherently will drop blood pressure. Arginine, Cit, nitrates, arginine, will all lend themselves to lower blood pressure. Drinking more water, more carbs are probably the best way for him to increase the pump if he really needs to...although I don't know why anyone REALLY needs to.
Has he tried dosing Resveratrol or Norvaline? I'm hesitant to suggest it because I don't know why his BP is low and it may be better for him to avoid, but these products will, in theory, reduce arginase levels and may "back door" what Agm. and Cit. accomplish.