Question: In Alchemy, the rules for what kinds of cards can replace a trashed card are governed by the following, somewhat ambiguous wording:

> 
> Adding coins to a cost doesn't affect [potion] being in the cost or
>  not. If [potion] was in the cost, it still is; if it wasn't, it still
>  isn't.
> 
> 
> 

The rules then present an example with Remodel card. However, the Remodel card says:

> 
> Gain a card costing *up to* two more . . .
> 
> 
> 

The Governor card wording is:

> 
> Gain a card costing exactly one (or two [if you're the player playing
>  the card]) more.
> 
> 
> 

So, for the player who played the Governor card, it is clear from the remodel example that a card costing exactly 2 coins must be replaced by a card costing exactly 4 coins with no potion.

However, what about a card costing exactly 2 coins and a potion? If trashed, must it be replaced with a card costing exactly 4 coins and a potion? Or could it also be replaced by a card costing exactly 4 coins (but with no potion)?

Answer: 
It must have a potion. The rule states that any time any cost is increased, the potion quantifier stays. Since the card you are trashing has one potion in the cost, the card you pick up also has to have one potion in its cost. For more strategy with this card (albeit not help with this particular question!) check [this](http://wiki.dominionstrategy.com/index.php/Governor) out.
Every card has two costs - its cost in coins, and its cost in potions. The total cost is the combination of the two. So cards like Governor that tell you to trash a card for a card costing "exactly 2 more" want the cost in coins to go up by two, and the cost in potions to be the same. Cards that talk about "up to" a certain cost may or may not include potions - Gold ($6) and Golem ($4+P) both cost less than Possession ($6+P), but neither costs more or less than the other. And if you trash a potion-cost card to something like Salvager or Forge, which explicitly mention "cost in coins", the potion effectively disappears.

So in your case, if you Governor a Scrying Pool ($2+P) you can get a Golem, but not a Scout ($4), but if you Remodeled it you could.