My Tahoe has made this sound since I bought the thing in 07 with 17 miles on it. Now it has 80,000 and still makes the exact same noise.
It's consistent with the RPM, its a kind of higher-pitched whining. Almost like a spool whining up. its very odd. I have custom exhaust so luckily its not too terribly noticible outside, but i have always heard it while driving and one of my friends has an 07 LTZ also and it doesnt make that noise. nothing at all is wrong with my tahoe as far as i know, everything is in perfect condition, had all services and oil changes etc.
dont know if it makes a difference, but my tahoe has every option that chevy offered at the time. they sold me on flex fuel (bull sh#$ since theres no flex station within 300 miles of me). one mechanic at the chevy dealer said it has to do with the flex fuel portion of the engine, but i know that not to be true because my friends tahoe is flex also.
i wish i could post a '.wav' file to preview the sound. its very unique. it almost sounds like a radio controlled car with a really loud motor. very odd. and yes im wanting to fix it 80,000 miles later lol
any ideas at all greatly appreciated! thx

 

I was told it is the fuel pump mine dose it to. Missed the consistant with rpm mine stays the same