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Old 04-28-2019, 05:44 PM   #65
Repeat LS3 Swapper
LS3goatee's Avatar
2004 GTO Owner

Join Date: Jul 2018
Location: Surprise, AZ.
Posts: 165
Premium Member

Swapped to a 3" Magnaflow exhaust! Had an exhaust shop cut the flange before the x-pipe off and replaced it with 3" pipe to make a true 3" system throughout (it choked down to a 2.5"(?) in that spot for some odd reason). I even got to add a bung to the hatless mids and move the AFR gauge up just a bit and my AFRs are now in line with commanded AFR via VCM scanner - It was back farther than it was supposed to be due to having to add a weld-less bung when I first finished the build. Unfortunately, my phone died halfway through so I wasn't able to take as much pictures as I am accustomed to taking whenever I change something on the car.

Mini review - only a short time driving. MY PREVIOUS EXHAUST SYSTEM was a custom 2.5" Borla ATAK setup. Loud and as raspy around 2k as the rapper Jadakiss! But rasp aside, the Borla setup sounded AMAZING, with ZERO drone. Another negative was the exhaust was done at a cheap shop and the welds were TERRIBLE, and the bends were extreme at certain points enough to be less than 2" in certain spots. The x-pipe was also on the smaller side, so I assumed all of these negatives contributed to the rasp. ON TO THE MAGNAFLOW. MAGNAFLOW COMPETITION SERIES 16734 First impression... QUIET AS A MOUSE. Wow. VERY QUIET. Which is what I wanted, but with the quietness came muffled definition, it doesn't sound like a small cam (like LS9 does) anymore like it did with the Borla ATAK, sounds like a stock exhaust system. Driving around the block after I noticed it was very metallic/tinny sounding. I was bummed. A highway drive produced some UNBEARABLE drone around 1700rpms, somewhat easily defeat-able by just going 5 over the speed limit cruising in 6th, or 70+mph. Very disappointed in the Magnaflow, but, I'll continue to drive it this week and maybe I will open up to it. I will commend the Magnaflow system because like 95% of the rasp is gone. Oddly enough, everyone else seems to enjoy it but me lol I will get some exhaust clips this week sometime. The biggest and most important takeaway from my swap to the Magnaflow is having a true 3" system from longtube collector to exhaust tip, with mandrel bends vs the shitty setup before, surely I got some gains up top. Here are some photos.

Exhaust work was done at Arizona Muffler
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04 Supercharged 6.2 GTO

Wealth of information creates poverty of the mind
LS3, LSA Blower, ZL1 lid, LS9 cam, Tick oil pump, Howards springs/pushrods, ARP goodies
Longtubes + Carven 3" exhaust, NW 92MM TB, Moroso catch can
Camaro SS Brembos F/R, 19" forged wheels, BMR skid plate, 05/06 rear bumper
Ron Davis radiator, Mishimoto Oil Cooler, ECU relocation, Tick adj. MC, SAP lower + CF Splitter
Gforce axles, Harrop diff cover, Megan coilovers
Custom Mavman CF cowl hood AND dash bezel

Last edited by LS3goatee; 04-28-2019 at 07:05 PM.
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