Mechanical stack injection is finickie to adjust.You have a high speed bypass and idle bypass to control excessive fuel,a main jet or pill controls the fuel feed,a slotted valve that increases the slot size is the throttle control.All the bypass and main feeds are controlled by pill size ,similar to jets.Many manufactures have modified these systems for better throttle characteristics.We just adjust for the best idle and maximum wide open throttle performance.We don't recommend mechanical stack injection for the street unless it is set up with a EFI system.