the text of this card say:

Rcommit, discard 1 momentum: after your opponent´s ready phase, until the beginning of your opponent´s next turn, all control checks get +1. if a player fail a control check, that player discard 1 momentum end their opponent adds the top card of their deck to their momentum.

for effect of this card, if my opponent play a card with a difficult of 6 and check 5, but he can pay with foundation for do it succeful, does he fail CC before paying the difference?

Thanks for yours answers.

More alongs the line of no. The checked has not failed after he flips the card. He still has the ability to commit the foundations to pass the check, unless u stun him to death or cc hack it so it doesn't matter.

I know where you were going with this, but unless the ability specifically states that you fail making the control check on the flip, your idea of exploiting dosn't happen. To view differences on control check flipping look at Miser, the new Rose and some of her support for details.

Stamp for Navidude.

You don't actually fail the check until you decline committing foundations.