2001 impala is losing power??

While driving i noticed the power was diminishing, i had to feather the gas to continue driving. I also heard a screeching noise which sounded like a fan belt . When i come to an incline, the car has zero power to make it up the hill now.  Any suggestions as to what has happened or is happening to my vehicle??

losing power- 1st thing that comes to mind is a clogged catalytic converter.

alright this is something to check that i had forgotten about, but what about the "fan belt" noise i heard shortly after it started??

well, theyre no longer called fan belts. The old days the engine had about 3 belts- fan, alternator/power steering/ AC.
maybe even 4. so the fan belt was specifically that- a fan belt... nowadays theres 1 giant belt that connects all these items. The Serpentine Belt.
Like a serpent cause it winds like a snake.....
 
Alot of these Serp belts will last a LONG time. The one in my Trailblazer is rated for 150K miles.... though Ive replaces it for peace of mind.
It could be that the belt has glazed over in some spots. But if its doing this every cold startup- it may either be the one of the pulleys- or the belt itself.
You can test this by grabbing a water bottle(spray). When you turn on the car and can sort of pinpoint the screech- spray some water on the belt- see if the noise goes away. if it does- then you know its the belt.
If it doesnt- then it may be one of the pulleys.
 

It could also be the belt tensioner that's noisey.

im with rbarrios, same thing happened to our car, its a bum catalytic converter. no power and noisey as hell

i know this is late reply, but here goes...
i bought a 2001 impala ls, used of course, anyway about 2 months later i experienced the same as you describe.
my problem turned out to be 2 coils  had gone bad, this caused no power nad under stress it made a nasty noise.
my chevy dealer fixed me up real nice, no charge.