Sc8P Mizer's second ability Is: R: After you opponent plays an ablility on a card in their staging area, make a control check. If you check X, negate the effects of that ability. X equals your opponent's card's control.

Can I tap foundations for this control check or is it just a straight control check that cannot be modified by committing foundations?

Committing foundations is done when you're checking against a difficulty in order to turn a fail into a pass , as with playing a card. Certain abilities that call for making a control check will tell you to check against a difficulty, for example Flowing Gale Hook.

Miser's text does not set any difficulty, so there is no pass/fail situation and no opportunity to commit foundations to make up the difference.

Note that committing foundations does not directly modify a check, all it does is turn a fail into a pass.