got this off of headers by ed site on shortys.
We do NOT make shorty headers as we know them to be considerably lacking in performance improvement capability (they cheat users out of good performance gains).
Note that for MOST applications - and this includes many forms of racing as well as street use - header tubes should be equal in length and 34" or longer as a header's ability to produce strong bottom end and mid-range power gains (in other words, produce a broad power band) is tightly linked to header tube length. Shorty headers don't come close to these design requirements - and, therefore, should be avoided at all costs IF maximum performance improvement is desired.