So I've been reading up on the forum posts so far, and I get that Youngster's ability requires the "Action" header. What I don't get is if PtL counts as having an "Action" header. On one hand, it's doesn't have the "Action" header. On the other hand, per the FAQ PtL specifically works with EI, which also (more explicitly then Youngster even) requires the same Action header.

Long story short, if PtL works with EI, can it also work with Youngster under identical logic?

No, PtL and EI do not have the "Action:" header. PtL and EI can't actually trigger each other directly, they're both triggered off of actions, for example:

I have Chewbacca equipped with PtL, Lando, and EI

1. Chewbacca performs any action (Focus), Chewbacca can now use PtL or EI.
2. Chewbacca uses EI to perform any action from an equipped upgrade card with the "Action:" header (Lando), Chewbacca can once again use PtL.
3. Before the stress from EI is assigned Chewbacca uses PtL to perform any action listed in his action bar (Target Lock)
4. Chewbacca receives the stress from both PtL and Ei.

So even though PtL was triggered as a result of using EI, it wasn't triggered by EI. The FAQ for this interaction was made because there was debate as to whether the stress from EI or PtL (whichever was used first) would be assigned before the other could be used (preventing a third action altogether).

Three of these cards belong together

Three of these cards are kinda the same

But one of these cards is doing its own thing

Now it's time to play our game

It's time to play our game

Three of these cards belong together

Three of these cards are kinda the same

But one of these cards is doing its own thing

Now it's time to play our game

It's time to play our game

Clearly, Expert Handling does not have an explosion in the picture.

Three of these cards belong together

Three of these cards are kinda the same

But one of these cards is doing its own thing

Now it's time to play our game

It's time to play our game

Clearly, Expert Handling does not have an explosion in the picture.

Nor does PTL. That's a planet. I think.

While PTL on youngster does nothing (no "action:" text), other ships in youngster's squad can benefit from PTL and youngster.

For example, Mauler with PTL, flying with youngster (with expose), can use Expose, then PTL to perform a focus action or something.

And FAQ states that Tie/FO ships can benefit from youngster too.

PTL and Experimental Interface are upgrades that allow you to perform extra actions.

However, neither PTL nor Ex Int are actions in and of themselves.

Ergo, they have no particular synergy with Youngster.

Aside from what treybert said.

EPT TIEs with Push the limit can get modified Expose Actions, etc.

Or Use expert handling to drop target locks while still being able to perform a 2nd action.

On a few ships like Mauler and Backstabber, getting up to 5 modified dice could be worth it.