For Concussion Missiles it says spend your TL and discard this card to perform this attack. I was under the impression that since the TL is being spent to perform the attack, you can't use it to modify the dice...can you?

Nope. That's why also having a focus token is a big deal.

If the TL is being spent to attack, you cannot use it to modify dice.

However, Homing Missiles, Ion Pulse Missiles, and Proton Rockets do not have you spend your relevant tokens, and you may therefore use them to modify the attack, or indeed save it for later in the round.

Some pilot abilities or upgrades can also supply additional tokens between when the attack is declared and when the dice are modified, and are therefore quite lovely.

So I have been doing it right then, I read a squad list post about getting extra actions to shoot more missiles and the way it was worded made it sound like you could use the TL on the attack. TY for the quick answer.

Notice the wording on Homing Missiles and Proton Rockets, those can often throw non-regular users of munitions off.

This is a classic case of just doing what the card says and not doing what it doesn't. If it says to spend the lock to fire then you no longer have a lock to spend to modify, if it doesn't say to spend the lock then you keep it until you spend it on something else, like modifying.

So I have been doing it right then, I read a squad list post about getting extra actions to shoot more missiles and the way it was worded made it sound like you could use the TL on the attack. TY for the quick answer.

If you're talking the Cracken missile swarm, no, the target locks are need to fire- the extra actions give the the target locks later, so you can wait for an elite pilot to come into range. it also lets you put focuses on each missile-firing ship, so pretty much every result on your concussion missiles are a hit. (concussion missiles turn 1 blank into a hit, so as long as you dont roll 2 or more blanks, that's 4 hits/3 hits+crit)