Flash of Insight on the stack.

[Harlequin]

Really quick question:

Flash of Insight   X1U
Instant
Essentially Impulse for X cards - what it does is more or less irrelevant.
Flashback - 1U,Remove X blue cards in your graveyard from the game.

When you play the card from your hand.  You anouce X and the converted mana cost of the spell is X + 2.  So If I declare that X = 2 then it would be countered by a chalice a 4, or drained for 4 mana.

When I play the card via Flashback, I still must anounce the value of X.  So agian lets say I say X = 2.  What is the mana cost of the spell on the stack.  Does chalice for 2 hit? or chalice for 4?  how much mana would I get from draining it?

[4-bar-killa]

The converted cost will also be 4. Because x is replaced by the number you choose when you announce the spell, overall on the card.
In the rules its written under x in the glossary:
While the spell or ability is on the stack, the in its mana cost equals the amount announced as part of playing the spell or ability.

[Godder]

The CMC of a spell with X in the cost includes X while the spell is on the stack. How X is paid doesn't affect the value of X, so the CMC of a flashed back Flash of Insight with X=2 will be 4.

[Harlequin]

What about flashing back Deep Analysis.  I thought when you flash it back, it took on the flashback cost.  whats a flashbacked Deep Analysis mana cost on the stack?

[asi]

The Mana cost is always what is printed on the right of the card name plus any values for X, Y, Z. That means for Deep Analysis, which makes it a card with a converted mana cost of four, no matter how you play it.

[Clariax]

Effects like flashback, or madness, change the cost to play a spell.  The same is true with effects that reduce costs (medallions, familiars) and effects which increase costs (sphere of resistence, etc.).  The mana cost, which is always what's printed in the upper right (barring copy effects), is the starting point when determining the cost to play a spell.  You start with the mana cost, you may end up replacing it with an alternate cost, increasing with addtional costs, reducing it.  By the time you come out with a final cost to play on the other end, it may bare little to no resemblence to the mana cost, but it still does not change the mana cost