You will have a hard time getting low end power from a bolt on...hearders, exhaust and any other bolt on are mainly upper power band gains ;-)! by the way 22hp on tb and plenum- bwhahahahahahahahahahahaahahah!! I know the accufab plenum is supposed to help all the way thru the power band, but I have one...and it doenst offer much gain but worth getting.
But, to answer your question...If you dont want to increase your cubic inches, or get a super charger....you should geta lower gear. Why do you want low end power so much? That is one of the great things about a mustang, they feel strong on bottom end for a 4.6L. motor. Stangs normally suffer on the big end.
