EFi live is by far the best tuneing for the dmax but it is a time consun=ming custom tuning software. It is not just a plug and play tuner. For efi try one of these two places they are by far the best in customer support and tuning support! Pat @
http://www.mcratracing.com/forum/ and Guy @
http://socaldiesel.com/ either one of these guys offer a great starter tune with efilive!!
For a good exhaust i recomend Mbrp 4" the 5" offers no more than looks to a lly IMO! Lots of supporting vendors here sell them try Pat or Larry @
http://discountpowerparts.com/