Hello
have an 02 silverado Z71 5.3 excab. A few months ago I noticed that when going up a steep grade it didn't have the power that it used to. I bought a Scan Gauge (http://www.scangauge.com/) and my torque never goes above 73 ftlbs. It doesn't matter if I am down to the floor or not. It hits 73 and thats it. The truck has a flowmaster 40 cat back kit and thats it. No other changes. I did put bosh double plat plugs in when I first bought it but I don't think that would have made a difference. Plugs do look good though. They are not burnt or loaded up.
Please help me.
Thanks.

 

most likely it is the plugs for some reason the 5.3 just want the stock ac delco plugs when i changed my plugs i best plugs in and it ran like crap and then i put the ac delco in it ran like a charm

 

basicly when it comes to plugs. ive been told so many times by all different people in auto shops that bosch plugs arent for american vehicles. acdelco works for the chevys and the pulsars but bosch. dont use em in the chevys. its funny yet proven.

 

Assuming you've changed your air filter,and you have no vacuum leaks, have you changed the transmission filter recently? Repair manual says it should be changed every 30k miles. You can get away with it for awhile, but the further you get past double the interval,(60k) the more it starts to dog you for mileage and power.

 

Ill try changing the plugs. It calls for acdelco 41-952 but all i can find is the iridium ones. I just replaced the trans filter afew weeks ago.
Thanks.

 

My '99 has a simular problem...I went to advanced Auto Parts, got the computer scanned, come to find out the catalytic converters are plugged. You may want to just have the computer scanned, could help you from possible headaches. Good luck!