2007 Silverado LTZ nbs 6.0L

When I am towing my fifth wheel I keep getting code P0011. It s fine while accelerating and driving but when I slow down to a crawl or stop, it throws the code.

I replaced Camshaft Position Actuator Solenoid Valve about 5000 miles ago
and the camshaft position sensor about 1000 miles ago.

I always synthetic oil, Deep Purple or Amsoil,

And help or suggestions on where I should start checking and looking next would be great.

Thanks