2025 2500HD ZR2 6.6L gas exhaust mod

[JoHURT]

need the opinion of someone sabby with the 2500HD 6.6L gas engine…
Traded in my 2022 5.3L Tahoe RST, had a true dual split Y-pipe, with an H-pipe into a dual inlet dual outlet Magnaflow and dumped before the axle.. ran phenomenal!! MPG’s and power band over all was spot on…
Thinking of doing the same to this new beast of mine, but it’s my first time owning a 6.6L and with the Alisson trans, my exhaust tech took one look underneath and saw what looks like a 3rd cat (no sensor attached) just after the Y-pipe, he began to tell me this speal about back pressure and if I split it as described previously as on my Tahoe I might lose rather than gain…
Okay fellas let the thread begin ….
I should also mention that my Tahoe had an AFE CAI, and a JET Performance MAF.. and the plan is to add those same upgrades to my ZR2 2500

and to make it clear, this is my daily driver and the suggested upgrades are solely to gain a bit more power to tug 37”s , overall better performance & MPG’s….

 

[KLA]

Good question. Waiting to hear people's opinions.

 

[AXE]

I would buy a complete system that is designed for the truck from one of the big companies that put in the testing and can show you any gains on a dyno. Gains are not likely to be noticeable on a big ol 8000+ lbs truck. But a dyno would show something even if it's 8-15 hp.

20% of at Hottexhaust.com

@SGRACING is probably the best guy to address this, as he builds performance motors and race rigs.

Hottexhaust

Find the best-fitting universal catalytic converters offered by HottExhaust. Explore high-quality MagnaFlow Products and Magnaflow catalytic converters online.

www.hottexhaust.com

 

[JoHURT]

I would buy a complete system that is designed for the truck from one of the big companies that put in the testing and can show you any gains on a dyno. Gains are not likely to be noticeable on a big ol 8000+ lbs truck. But a dyno would show something even if it's 8-15 hp.

20% of at Hottexhaust.com

@SGRACING is probably the best guy to address this, as he builds performance motors and race rigs.

Hottexhaust

Find the best-fitting universal catalytic converters offered by HottExhaust. Explore high-quality MagnaFlow Products and Magnaflow catalytic converters online.

www.hottexhaust.com

What’s your take @SIGRACING regarding my forum topic ?

 

[Roach769]

Also super interested in @SGRACING's take on this.

 

[bmcmay]

Good morning,
By chance any progress on this? I just purchased ZR2 2500 traded in my AT4HD 2500 I had put a MBRP stainless steel cat back system sounded great, just need to do the same to the ZR2. I checked with MBRP, BORLA, MAGNUM flow...nothing because of the suspension/shocks are in the way I was told. They have to create a need angle.

 

[AXE]

Good morning,
By chance any progress on this? I just purchased ZR2 2500 traded in my AT4HD 2500 I had put a MBRP stainless steel cat back system sounded great, just need to do the same to the ZR2. I checked with MBRP, BORLA, MAGNUM flow...nothing because of the suspension/shocks are in the way I was told. They have to create a need angle.

Any exhaust shop can do the necessary piping. There's plenty of videos on YouTube of 2500HD gassers with new exhausts.

 

[JoHURT]

Any exhaust shop can do the necessary piping. There's plenty of bodies in YouTube of 2500HD gassers with new exhausts.

Yeah, so I ended up cutting out the 3rd cat and replacing with the same 3 1/2” pipe, removed the factory muffler and went with a Borla 3 1/2” truck 24” muffler, I cut the tailpipe and dumped it right after the rear axle. I also installed MSD’s blaster coils, Moroso Ultra 40 8.5mm wires and a set of AFE stainless steel headers…. No lie, 35-40% gain in MPG’s and not too loud which is what I wanted. I don’t like loud “Takuache” annoying exhaust. Truck runs beautifully, I wasn’t looking at increasing horsepower cause my intention is to not race this 8000lb tank but to gain its full power potential

 

[JoHURT]

Yeah, so I ended up cutting out the 3rd cat and replacing with the same 3 1/2” pipe, removed the factory muffler and went with a Borla 3 1/2” truck 24” muffler, I cut the tailpipe and dumped it right after the rear axle. I also installed MSD’s blaster coils, Moroso Ultra 40 8.5mm wires and a set of AFE stainless steel headers…. No lie, 35-40% gain in MPG’s and not too loud which is what I wanted. I don’t like loud “Takuache” annoying exhaust. Truck runs beautifully, I wasn’t looking at increasing horsepower cause my intention is to not race this 8000lb tank but to gain its full power potential

Forgot to mention I also installed an AFE cold air intake and swapped my mass airflow sensor with a JET Performance MAF

 

[bmcmay]

Forgot to mention I also installed an AFE cold air intake and swapped my mass airflow sensor with a JET Performance MAF

Thank you for responding. You put a lot of work! Thank you again.