There is a hissing noise only while accelerating between 2000 to 2400 RPM coming from the engine area. It is only under load. Not in gear, increasing engine speed from 2000-2400rpm is not creating the noise.
Thank you!
How many miles and year of manufacture can greatly enhance diagnosis. Hissing typical of a vacuum leak - not uncommon before EFI days. Consider a faulty engine air filter install or a torque converter if around 180k miles.
About 120k miles. Is there any system that is activated via vacuum in at that engine speed, during acceleration? Thank you for your help!