Engine pops (fuel related?)

Hello,  I have a questioned for the seasoned professionals
 
I own a 1971 Jimmy with a 350 engine and some aftermarket edlebock carb
 
The engine idles fine but here is my problem
 
From a stop if I push the gas too much the engine kind of stalls for a bit then catches up with itself and runs fine
 
also  let’s say I'm doing 40 mph  and I push the gas a little more to gain some speed-   the engine will start to pop lake crazy kind of like it backfires   but if I stomp it to the floor the engine goes and performs like normal... Any ideas as to what could be causing this?
 
Thanks

It sounds like the carb is probably running lean. Try opening the air fuel mixture screws 1/2 a turn each and see if that makes a difference.