What's the 2006 Chevy silverado vortec max horsepower?

The 2005 Chevy Silverado with the 6.0L vortec V8 makeS345 horsepower and 380 pound feet of torque. This is a fair amount for a V8 engine and should be enough to drive Your truck at highway speeds with no problems. If You do want more power out of Your engine there are some things You can do to it. There are aftermarket intakes and exhausts that can increase horsepower and throttle response. There are also some tunes that are available and these can also increase the power output from Your engine. The important thing to remember whenever You modify components in Your engine though is that it will cause more strain on the engine components.