I know my sig is a 6.7 but I need to ask some 5.9er's about an afermarket plenum. I noticed that I gained 4psi of boost and my idle egt's are about 50° lower than stock. Also at 100mph with the edge turned up my temp was 1050°, so im happy there. But I noticed that the egt's fluctuate really fast and it climbed up to 1500° and just as soon as it does it drops once the truck catches up with the throttle. I will post some pics of it later but I know the truck pulls better especially on take off. My whole theory is that more air means more fuel has to be added so there will be a temporary gain until she levels out. Btw the intake is super smooth, i've just never experienced a new plenum, and advice will help and what alhave y'all heard or experienced

Thanks
Dayton

 

get more results being in the 5.9 section.

in reality you should not have seen any boost gain as boost is a measurement of restriction and with reduced restriction it would drop slightly. i can see a temp drop.

as with your theory more air = more fuel. unless you did turbo and fuel mods, it has not changed