Retuning the de-tuned V6 should unlock useable power.
If you pick up an all-wheel-drive 2021 Lexus IS 300 rather than the standard rear-wheel-drive model, for an extra $2,000 you're also getting a 3.5-liter V6 engine rather than the four-cylinder turbocharged 2.0-liter lump. That's quite a bargain for a car we like a lot, and gets you a useful 260 horsepower and 236 lb-ft of torque. However, you could also go for the lighter Lexus IS 350 and get another 51 horses and 44 lb-ft of torque. However, the all-wheel-drive IS 300 sprints its way to 60 mph in the same 5.7 seconds and is just 0.1 of a second slower on the quarter-mile. That should get any tuner stroking their chin and seeing a dyno in the IS 300 AWD's future.
If you could add that 51 hp and 44 lb-ft of torque from the identical IS350 engine to the all-wheel-drive LS300, then you would have a subtle sleeper on your hands. Motortrend brought this up with Dennis Knatt, the owner of D3 Performance, who told the publication it is do-able and "I know that the [two model's ECU] tables are basically the same." The tuner already offers a solution for the rear-wheel-drive IS 350 for $600, adding up to 24 hp to the power curve. He believes he could do the same with the IS 300 but needs a loaner car and access to dyno equipment built for all-wheel-drive vehicles for a couple of weeks.
Thankfully, there are a plethora of tuners out there, and sooner or later, someone will come up with a saleable solution to re-tune the IS 300's detuned engine. They will likely also add power over the top and close the straight-line power gap between the IS300 AWD and the IS 350 F Sport with its 311 hp and 280 lb-ft torque.
That would make the subtly bodied IS 300 in all-wheel-drive form a bit of a wolf in sheep's clothing. With some mechanical modifications to make it breathe easier, it could become a little rocket ship for embarrassing much more expensively badged cars. Once tuners start offering solid solutions, we expect the IS 300 to become a popular car on the used market over the coming years.