Question: Does the wording on the engine upgrade card say it adds the [boost] icon to your action bar?

Could you equip autothrusters if you also have an EU equipped?

Edit:

ANSWER: They're both modifications. I'm dumb.

Both are modifications, so no.

Except for interceptors,but they already have boost.

So, no.

They're both modifications, so no.

Only interceptors get two mods and they already have boost.

Question: Does the wording on the engine upgrade card say it adds the [boost] icon to your action bar?

Could you equip autothrusters if you also have an EU equipped?

Yes, you only Royal Guard Ties can equip two modificatons.

Question: Does the wording on the engine upgrade card say it adds the [boost] icon to your action bar?

Could you equip autothrusters if you also have an EU equipped?

They are both Modifications. The only ship that could actually take them both at the same time has Boost as an action natively.

If it were possible to equip both on a ship that didn't have Boost I would think that it would be legal.