Modified Stock Carb

What exactly is done to the stock carb to modify it and does it make a BIG difference.

[Tommy 17]

well mines mod and i don't know exactly whats done to it... but when u look inside it it looks like a tornado... it has swirles in it... also u can remove the choke... it costs like 80$ to get done...

Normally they bore/hone it out and remove the choke.

[Sparky416ex]

yeah i heard some where you could bore out your carb how much HP does it give you