Is this card too good?

Yes. It's better than Ancient Tomb, which is way too good.

So is this the same as ", Pay 4 life:" ?

The problem with this kind of card is that you have to keep nerfing it and nerfing it until it's only any use in the cases where it's still broken. If you make a card with so many drawbacks that the only decks that can cope with it are so blisteringly fast that they can ignore it, haven't you just made a card that's useless 95% of the time and worryingly good 5% of the time?

Put another way, who is this card aimed at? At the moment it'll only be used at all in extremely aggressive red decks. And yet it could still be warpingly good in those.

Make it more red then, it's a common and thats to good btw.

~ Etbs tapped. ~ doesn't untap during your untap step.

Whenever a red spell you control deals damage to an opponent, untap ~.

­: Add to your mana pool.

If you put it that way, then suddenly Grapeshot becomes insane mana acceleration.

"If you are playing the correct deck, every spell you cast gives back 2 mana" is a bit too good, yeah.

For what it's worth, making a land that produces two mana and isn't broken or breaks your heart when you read it is a crazy difficult challenge, and many designers have spent far too many hours trying to figure out a way to do it. Temple of the False God seems to be the best solution to the problem, IMHO, since it neuters the broken mechanic (fast mana), but still provides something of value (the mana bump on round 5 is still a solid bump). If you can find a way to tap into that vein (For example, add to your mana pool. Activate this ability only if you dealt 3 or more damage to a player this turn.) the end result wouldn't cause as many negative reactions from 'developers'.

Costs can't target. Neither can mana abilities, or they're not mana abilities.