Sup guys ok so I got a 5.3 with a 218/228 .550 cam, .015 milled 862 heads, headers, CAI. It's not tuned. So only at a low rpm ( 600-850) when I give it like 30% - 40% throttle it sputters then back fires then takes off only at that rpm though. I have no idea what's going on

 

It's not tuned.

 

So that's. why its doing that ?

 

My guess it's a lean backfire, given everything is good mechanically.

Is it in an F body?

 

Yea everything mechanically is good And no it's in a truck