With our 1 warm day yesterday I was able to get the car out for a drive with the top off. With new Shell 93 fuel and a recent Chevron fuel system flush I notice the engine sounds like it's running on low octane gas when I goose the motor.
I found this on MYCARSTATS and was wondering if it was the same thing:
SERVICE BULLETIN:3237 NHTSA ITEM NUMBER:10011733
MFG Bulletin Date: 19010101
Component: ENGINE AND ENGINE COOLING
Bulletin Summary: 700-900 RPM BUZZ MOAN RATTLE RESONANCE NOISE ON ACCELERATION. *EH
Date added to datbase: 20050131
We have an appointment at the dealer for Saturday but if we get the 3" of snow they are predicting I'll have to put it off.
I've also noticed in colder weather the engine has a slight diesel sound, mostly when it's cold. Are these common issues to this car?

 

www.pistonslap.com Is very common and more so with cold. The humm, I have no clue, sorry.

 

This is all I could find under the TSB "buzz" Word

97-05 Chevrolet Corvette 6-Speed Shifter Rattle Growl Buzz Noise - kw 5.7 6sp boom clash clutch diagnostics gear late lazy LO4 LS1 manual MM6 MN6 M12 neutral noise pinion rattle shake shift shifter #PIP3104A - (Aug 18, 2004)
97-05 Chevrolet Corvette 6-Speed Shifter Rattle Growl Buzz Noise
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The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:
Condition 1. 97-04 Corvette:

Shifter buzz noise at approximately 3000 RPM.

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Condition 2. 97-05 Corvette:

Gear rattle or buzz noise at low RPM (below 1500 lugging the engine) or during engine shut down. Also neutral gear rattle noise with the transmission in neutral and the clutch engaged. These noises may be worse with the air condition compressor engaged.

Recommendation/Instructions:
Condition 1. 97-04 Corvette:

A revised shifter assembly with added isolation bushings is available as part number 10331311. Part numbers are subject to change so please use any updated part numbers if any become available.

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Condition 2. 97-05 Corvette:

Gear rattle or buzz noise at low RPM (below 1500 lugging the engine), during engine shut down or also neutral gear rattle noise with the transmission in neutral and the clutch engaged are all normal operating characteristics of the 6-speed transmission. No repair attempts should be made on these conditions. Please refer to informational service bulletin 03-07-29-004 which discusses normal operating characteristics of manual transmissions.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:
(97-05 Chevrolet Corvette)

 

Not so much a buzz as a pre-ignition jingling the valves make when you have bad gas. Plus the clacking noise a diesel makes, but not all the time.
Wonder if it's just in need of a valve adjustment?