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Message: [QUOTE="Wayne, post: 245711, member: 863"] power fell off after 3500 likely due to back pressure and air flow capability of the turbo at elevation. an 82 mm precision turbo we tested later in the day carried the power band @ 700 rpms past where this one fell off. heads have heavy duty springs, but stock flow The original cam in the built motor Aaron had started out as a stage 3, then switched to a stage 2. Too much valve overlap (causing compression drop) for lighting the turbos he ran in a reasonable amount of time The one in Tadd's truck is a stage 2+, which is stage 2 duration (no valve overlap) with stage 3 lift. The cam in the engine only hurts power below 2000 rpm's, but carries the power band much further than a stock cam. Seeing as how at this altitude the S475 doesn't start to build much boost until 2500+ rpm's it's hard to consider the cam as problematic for the setup. We have run the stage 2 cam in a good handful of 6.0's and 6.4's with excellent street manners at both low and high rpm's. It is by no means a dramatic power loss at less than 2000 rpm's with properly sized turbos. For guys running big turbos, who have stock stall converters, and have difficulty lighting their charger/chargers before their cam will have a bigger problem if the converter isn't loosened properly. Cruising at 2000 rpm's, the S475 setup only builds about 2 psi of boost. When cruising down the freeway at 2500 rpm's, and you mash the throttle there's a good amount of smoke (see vids posted previously), but HO-LEE-CRAP! The truck really sucks you back in the seat at that point (what do you expect? it's 750+ hp, and the truck is considerably light (SCSB). The engine definitely has more fuel than the S475 can use at this altitude running "extreme race" programming, which is why the power dropped off going with the more agressive tuning. With custom tuning I'm sure a little more power could be squeezed out of it. Keep in mind though, the testing wasn't to prove how amazing the MPD setup is. This testing was done to compare the turbo included in the kit with a comparable precision unit. Hopefully this info helps people understand. [/QUOTE]