GM-GMC: power loss, gmc z71, catylitic converters

Question
2002 GMC Z71  33,000 miles.   I have found that when I drive my truck, before when I pull out i had to give it a little amount of gas to turn the tires over.  Now I can take off from a dead stop and it wont turn the tires over at all.  When towing my boat i had no trouble with pulling it up hills or from red lights.  Now when i go up a hill the truck slows down and hold a steady speed.  I feels like I have lost about 50+ horse power  

Answer
there are many reasons why you may feel a power loss. Here's a list  to kinda start from. lack of air flow, lack of fuel presure (pump or fuel filter) lack of exhaust (too much back presure....blocked cat)poor gas, poor o2 sensor response, engine timing retard (knock sensors), tune up parts(plugs and wires) i have had to change many catylitic converters ont these trucks !  the may be other things as well but these are the most comon   check it out