If a permanent has an activated ability with an untap cost and a mana ability with a tap cost, xMage incorrectly allows you to pay the untap cost and then use the mana ability to pay for the rest of the cost

For instance, if [[Mairsil, the Pretender]] has exiled [[Gilded Lotus]] and [[Pili-Pala]], starting from tapped, xMage allows you to activate Pili-Pala's untap ability, and then tap mairsil for Gilded Lotus' ability to pay for the mana cost of pili-pala's ability. But the rules have this to say:

> **601.2g** If the total cost includes a mana payment, the player then has a chance to activate mana abilities (see rule 605, “Mana Abilities”). _Mana abilities must be activated before costs are paid_.

(emphasis mine)

So once I started paying the costs (untapping with the untap symbol) I should no longer be allowed to activate mana abilities.