there is a group buy in the works for a short shgifter from korea
www.rdtiburon.com (go to the group buy section in the forum)
you can type in "obx tiburon" on ebay in the search box and find some headers, and a cat back exhaust for about 400 altogether. he has made a lot of deals with tiburon owners and so far, only good things come from customers. there are also a lot of cold air intakes on ebay that work almost just as well as the aem one.
so for about 650(max) altogether, you can get an adjustable shifter, headers, catback exhaust, and a CAI. these things will add about 20 hp at the wheels alltogether, and very short shifts.