Complaint was uneven heat on 3 burner grill m# sg-36 S# 951393634 south bend. Jb style valves, when set on 300*f Left is 355 middle 400 right is 300. left and middle have a standby flame adjustment. Right valve does not. adjusted standby flame and checked gas pressures. when all off 6 in wc and a drop of 2 per burner when fully on. I suspect a faulty pressure regulator but how much drop should there be when all open. And what is the best way to calibrate this style.