If I use Dash for the Pilot, Leebo for the crew, and a Engine upgrade for the mod can I boost twice in one round?

Thanks in advance.

No - Leebo allows a free Boost action. You cannot take the same action multiple times in a round, regardless of the source of the second action.

Thank you!

OK so you do get 2 actions with Leebo as co-pilot/crew? You just can't pick boost as your 1st action.

With the setup above, your choice of action in the Perform Action step would be Focus, Target Lock, Barrel Roll, Boost (from EU) or Leebo (a Boost which gives you an Ion token).

If you take a Boost action in the Perform Action step, you will still need to somehow acquire the ability to perform another action (like from Squad Leader or Push the Limit), but because you've already boosted this round, you won't be able to use Leebo's action.

Leebo's free boost action doesn't mean you get automatically two actions each turn either. It's described as a "free" boost action so a ship without the boost icon (like the YT-2400) can still use it, which means you wouldn't need the Engine Upgrade if you had Leebo as crew. So taking Engine Upgrade and Leebo is doubling up needlessly.

Thanks I guess the free boost kind of threw me.

OK so you do get 2 actions with Leebo as co-pilot/crew?

Technically, yes you do. The 1st action is from the crew card which starts with the header "Action:" Part of that "Leebo action" is a free boost action. That's the 2nd action.