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: 
@JHaasie77's answer is spot on, I just want to add another way to think about it that grew too long for a comment.

Costs with potions are like complex numbers, with the potion cost corresponding to the imaginary part. The now-defunct Isotropic online Dominion server handled this quite nicely using `p` to designate potions. If you played 3 Coppers and 2 Potions, Isotropic would report the amount of money you have to spend as `3+2p` (or something like that).

Using this analogy, University costs `2+p`, and `Governor`ing a University calls for adding exactly 1 (or 2 if you're the player playing the card) to the cost. Thus the card you gain from trashing a University to a Governor must be exactly `2+p+1 = 3+p` (or if you played the Governor, `2+p+2 = 4+p`).

The analogy isn't perfect for cards like Remodel specifying "costing up to `x` more", but it's workable. The "up to" applies to both coin part and to potion part. Remodeling a University lets you gain a card costing up to `2+p+2 = 4+p`, so up to `4` in coin cost, and up to `1` in potion cost.
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.