yruh8n
+1y
i had a 94' GMC crew cab dually with the 6.5 in it. the pmd and injection pump goin out is a pain in the butt, i even movied the pmd and it still went out. as with any diesel you need to open it up to move air, more air in and more air out. unless things have changed the biggest turbo downpipe for this motor is a 3", you can put a 4" past the down pipe but you still have the restriction of the 3" at the down pipe. but in all honesty anything over the 3" past the down pipe is just over kill. i have a 7.3 powerstroke now and the biggest turbo down pipe that will fit is a 4", so i am running a 4" from the turbo all the way out. you can also get chips for the 6.5, i had one in mine and it made some difference in the performance, i would recommend getting one. if you start adding performance to a diesel you will need to get some gauges to keep an eye on exhaust temp, turbo/boost pressure, and trans temp.