need advice on what could cause this slight engine problem

if I'm cruising at city speeds like 30mph and i step into the throttle to wot i get a slight bog but when im cruising at 50mph or higher and i do the same i dont get a bog and its very smooth.

So i'm thinking i need to change the pump shot but not sure exactly which way to go with it (sooner vs later or more vs less)

99% of the time flat spots mean lean.

Go up one size in the squirter.