A - are you both R8? If not he may have recently upgraded Piett to R9 and that's why he's always beating you to first turn.
B - if not A, then do you have all 6E or better mods on Piett? Does he? This also affects the final ship speed.
C - always call in Ebon as your first reinforcement. You'll massively delay their ultimate and hopefully get to yours first. Use Ebon's basic only to grant an ally 15% TM with each hit. If he calls in Boba you can use the middle special to cleanse the buffs off Boba but it's usually not needed. Only use the third ability if you need to reapply chaff to your team.