Anytime you can move more air you will lower egt. You could try goin the t4 route with an s468. The 6 speed makes it a little more difficult because too loose exhaust housin (1.15) and it might not spool and the luggin will make egt high. Too tight (.90) and back pressure and egt will become a problem. With 100% nozzles, a 38r should be about to keep them cool. What's your elevation? Do you have big lift and tires? are you sure you don't have any exhaust or boost leaks. Lots of things i would do before spendin 3-4k on a new turbo set up