Ok,Ok...I know ,search other threads first, and I did, but there are many different answers to this..not much found that is definitive...I've got an '03 GT 4.6, all stock. I'm gonna bet 50% say 19lb hr, 27% say 21lb hr and23% say 21.5!! I've also seen that the ECM makes up the diff between 19 and 21lb hr.:sorry..this can be frustrating!! I appreciate any help you all can give. I need to know to send the info to SCT to allow tuning parameters...and it seems there could be 19's or 21's depending on mid year production???...Thanks!! I've got some mods planned and this will help...