L5P Downpipe: Is it worth the headache for the extra flow?

[DieselDyno_Mike]

I’m looking to pull more power out of my L5P. I’ve seen people replace the restrictive factory downpipe. How much EGT (Exhaust Gas Temp) drop are we actually talking about here? And does it make the turbo whistle sound cooler?

 

[TorqueCurve_Ace]

The EGT drop is real, especially when you're under heavy load. On my '19 L5P, I saw a consistent 100-150°F drop on long uphill pulls towing my 5th wheel. The factory pipe has a massive pinch point that just traps heat.

 

[Lucas]

It's one of those 'support' mods that people ignore until they start running hotter tunes. If you're staying stock or running a very light tow tune, you might not notice a huge difference. But as soon as you add more fuel and boost, that factory downpipe becomes the wall you hit. The EGT drop is just a side effect of the turbo being able to breathe. It’s all about efficiency—less backpressure means less heat soak, which lets the truck hold peak power longer.

 

[DieselGearhead]

The EGT drop is significant when you’re pulling a load, but the biggest benefit is really the drop in drive pressure. The factory pipe has a really tight crush in the casting right after the turbo exit. Once you open that up, the turbo doesn’t have to work as hard to maintain boost. I monitored mine with a probe before and after—under a 10k lb load, I consistently saw a 100-125°F reduction in EGTs. It’s not a 'feel it in the seat of your pants' power mod, but it’s a 'don't melt your turbo' reliability mod.

 

[DynoDaily]

If you’re doing it for the sound, prepare for a surprise. It’s not just a 'cooler' whistle; it’s a much sharper, more aggressive spool. At low RPMs, you can really hear the turbo moving air, and during deceleration, that 'jet engine' sound is way more pronounced. Just keep in mind that since the downpipe removes that bottleneck, you might hear a bit more engine noise in the cabin overall, but the turbo sound is definitely worth it if you’re a fan.