U gotta hit and run
If you're not already using high-I separatists, consider using the I3 generics over I1s, so you can make it harder for the Y-wings to get those locks. Then, you just crash in on a Y-wing and I-kill it, then you blast out of there before the other ones can turn around on you. (Note, "blast out of there" can also mean "get in too close for them to turn around without K-turning")