Equipped with a 6.2-liter EcoTec3 V8 and a ten-speed automatic transmission, the brand new 2021 Chevrolet Tahoe is rated at 420 horsepower and 460 lb-ft of torque at the crank - more than enough get-up-and-go for the average SUV shopper with a predisposition for towing. Of course, for some, "sufficient" will never be enough; no matter the vehicle, there will always be those who won't rest until they've squeezed every last drop of performance out of a factory-stock powertrain.

Unfortunately, GM is determined to make that a difficult task with its new vehicles, introducing a tricky new electrical architecture in models like the 2020 Chevrolet Corvette C8 and the 2021 Chevrolet Tahoe that's said to be virtually "unhackable". Power aficionados hoping to tune the new GM full-size SUVs to the moon and back should consider looking elsewhere.

American tuning firm Hennessey Performance Engineering bemoaned the issue on YouTube recently, writing "we hope that GM will consider working with SEMA and the aftermarket industry to come up with a tuning solution for these vehicles. But for now and the foreseeable future, stock power is about all you're going to get out of their new vehicles."

But do GM's factory output ratings actually hold up to scrutiny? Hennessey strapped its new 2021 Chevrolet Tahoe High Country to the dyno to find out, and the results were about where you'd expect: 369 horsepower and 397 lb-ft of torque at the rear wheels. That translates to about a 12-to-14-percent parasitic loss, assuming GM's numbers are accurate, which sounds very plausible.

Of course, the fact that Hennessey Performance Engineering has a 2021 Chevrolet Tahoe to test suggests that the tuning firm is cooking up some upgrades regardless of the vehicle's tunability. The company specifically mentioned cold-air intakes and cat-back exhaust systems as examples of mods that could be applied even without access to ECU remapping.

As for a super-high-powered supercharger package in the typical Hennessey fashion, that might have to wait.