[chewster]

97 de ville (base model) with 105,999 on NS.
high pitched hissing/howling noise under the hood, seems to be coming from
driver side, cant quit pin point the exact location. noise seems to only be
heard during accelaration. also noticed hesitation at 50-55mph.
any suggestions you guys can give...

 

[Ranger]

Hissing sounds like a vacuum leak. Drivers side, maybe brake booster. Use a stethescope or in the absence of one, a lenght of hose to your ear and listen around. That will help pinpoint it, much like a geiger counter.

Howling makes me think bearing. In which case I would say look in the vicinity of the water pump tensioner.