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I wanted to make a post to see if anyone has had similar issues because as it seems right now, no one has answers.
2019 GT63s tuned by ECC slav CPC, TCU, intake, downpipe, GFB valves, tuned on 93 octane. Datalogged it right after getting flashed and Slav said it was cutting power top end due to bad fuel, went to another gas station and logged it, and was still cutting power top end. Filled it again with 93 from a different gas station (this time a reputable Sunoco), and sure enough after logging it, still pulling timing on the 93 map. Recently filled it with 98 octane Sunoco 260gtx, still cutting power.
running consistent high 8s 60-130 via dragy (attached), even on the 98 octane, which is slower than it runs stock. Spark plugs were done by Mercedes less than 8k miles ago, logged the IATs and those don’t seem to be an issue either. Also reset adaptations by flashing it back to stock, driving 50 miles and flashing the tune again, which I was told to do by ecc slav, still no fix. Also ran it on a 91 map, same results.
Very desperate looking for answers if anyone has any insight it was be appreciated!
Last edited by Andrewgt63; Jun 15, 2025 at 06:26 PM.
2025 AMG G 63 SUV /// 2025 AMG GT 63 S E Performance 4 Door Coupé
Have you checked the fuel filter, fuel pump, oxygen sensors and injectors for any issues? You could be “creating” a bad fuel code if there’s issues with these components. Also, I assume you’re doing said pulls with a sufficient fuel amount in the system. Doing WOT pulls with low fuel can strain the pump to the point of power loss and code throwing.
I wanted to make a post to see if anyone has had similar issues because as it seems right now, no one has answers.
2019 GT63s tuned by ECC slav CPC, TCU, intake, downpipe, GFB valves, tuned on 93 octane. Datalogged it right after getting flashed and Slav said it was cutting power top end due to bad fuel, went to another gas station and logged it, and was still cutting power top end. Filled it again with 93 from a different gas station (this time a reputable Sunoco), and sure enough after logging it, still pulling timing on the 93 map. Recently filled it with 98 octane Sunoco 260gtx, still cutting power.
running consistent high 8s 60-130 via dragy (attached), even on the 98 octane, which is slower than it runs stock. Spark plugs were done by Mercedes less than 8k miles ago, logged the IATs and those don’t seem to be an issue either. Also reset adaptations by flashing it back to stock, driving 50 miles and flashing the tune again, which I was told to do by ecc slav, still no fix. Also ran it on a 91 map, same results.
Very desperate looking for answers if anyone has any insight it was be appreciated!
It sounds like a classic case of the car's safety systems intervening. Since it's happening across multiple fuel types and maps, the issue is likely mechanical, not tune-related.
The most common culprit on the M177 is the fuel pressure sensor. It's a known weak point and fails often. When it goes, it provides incorrect data, causing the DME to pull timing and cut power to protect the engine.
Get the fault codes read, even if no dash light is on. A deep-level scan with a capable tool like Autel or Vediamo will likely reveal hidden codes related to low fuel pressure or sensor plausibility. Replace the fuel pressure sensor first; it's a cheap and common fix.
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