The ability on IG88b (dont have the card in front of me but pretty sure it is that one) states if you miss you can attack again. The question coming up at our game nights is does the target of the second attack have to be the same as the first, because it does not state that it does?

... because it does not state that it does?

You've answered your own question. The card doesn't say you have to attack the same target, therefore you don't.

So i also noticed that gunner and luke co-pilot cards also do not state it must be on the same target, so do they also get to attack a different target because i was under the impression that those ones had to be the same target?

No, there has never been any requirement for that to occur. It says to perform a second attack, which means that you go through all 7 steps of attack, which includes selecting a valid target.