Exhaust like odor when accelerating at highway speeds

[Pete Sabine]

My friend recently purchased a 2021 RX 350 gas model with less than 5k on the odometer. The car now has 10k miles and when accelerating on the freeway onramp or highway speeds there is a an exhaust like odor inside the car. 

She took the car to the dealer who confirmed the odor from the test drive and told her the cause of the odor might be sediment in the fuel tank from the previous owner not driving the car very often and/or at highway speeds. The service manager offered no solution except to drive the car more aggressively and maybe the sediment will dissipate and eliminate the exhaust odor. 

If this theory is correct, then why not drain the fuel tank and purge the fuel system under factory warranty instead of making the owner suffer driving the car with a pungent odor?

Any input is greatly appreciated. 

Edited September 5 by Pete Sabine
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[LexusGenesis]

The dealer seems like they don't want to work on it.  I don't see how sediment would cause any odor.  Why would it have any to begin with, having so low of miles.  If the exhaust is being smelled in the cabin then some exhaust fitting is loose and they need to address it.  Besides making you sick and dizzy and a safety issue.   Take it to another dealer, and have them fix it, or take it up the chain of command and find someone else, that willing to do their job.  Sorry, you have to deal with that.