It has a manual transmission.

Yes, noises are difficult. [GG]

I was hoping that perhaps the specific rpm and the fact that it occurs at
that rpm only while there is a "demand" on the engine (pushing the
accelerator) might point to a known historical possibility.

Thanks!

Best regards,

Scott

Could be a total coincidence - hard to say.

Perhaps buy a cheap automotive stethoscope and probe around. It could
be a bearing in the AC or steering pump (possibly water pump - I
wouldn't exclude it just because it is new). Maybe the timing belt
idler has a bad bearing.

If it is an automatic, also probe around where the transmission and
engine meet up (drive plate and torque converter). Sometimes the bolts
that hold these things together slowly walk themselves out and can
cause resonance at certain speeds.

There are many other things that could cause resonant noise like this -
others here will have more suggestions, I am sure.

Remco

Last summer had the Timing Belt and Water Pump replaced in my '97 del Sol Si
(95000 miles at that time).  While in the shop for this preventive
maintenance also had the shop adjust the valves and other tune-up items).
Since that time we have noticed a noise at about 2500 rpm coming from the
engine compartment.  At first it wasn't too bad but it seems to be getting
louder (colder weather a factor?).  The noise only seems to occur at about
2500 rpm when the car is under load (pushing down on the accelerator).

Any thoughts?  Is the maintenance done last summer a clue or is that just a
coincidence?

Scott