Bad fuel economy 2011 5.3 afm

[Patrick Dolan]

I gots this 2011 5.3 and the economy took a crap on me I was getting 18 town before I hit 100k and now ima getting 10 n 12 highway wear I was getting a good 21 b4...I changed all lifters, valves, intake manifold, and all gaskets nd all my injectors are good no vacuum leaks anyone had problems like this I got the cylinder deactivation system in it aswell ima like wtf I literally get 60 miles per quarter tank on the highway doin 65 any one have similar problemss

[DaveH71]

Tune up?

[BlackZ71Silverado]

Wrong Forum.................................