The Holy Spirit through The Church, of which I am a member.
The Mormons say they are assured that they are right because of "the burning in their breast."
Experience and alleged supernatural revelation is not a very strong argument. Every mystically-inclined religious person - whether Protestant, Catholic, Mormon, or even Islamic - can make an existential argument. Such an argument is therefore highly dubious, if not worthless.
Yes, the Holy Spirit DOES come to us through the Church. So why do you disagree with some of what the Holy Spirit teaches His Church, in some cases, for 2000 years? Is the Spirit teaching men different teachings, or are men following their own fancies?
Regards