I fail to see how the presence of Christ is different in the Mass [and we can debate the Mass later] as opposed to what John wrote in 1 John:
By this we know that we abide in Him and He in us, because He has given us of His Spirit. 1 John 4:13 NASB
The word in (ev in greek) can convey the meaning of:
of a person to whom another is wholly joined and to whose power and. influence he is subject, so that the former may be likened to the place in which the latter lives and moves. So used in the writings of Paul and of John particularly of intimate relationship with God or with Christ, and for the most part involving contextually the idea of power and blessing resulting from that union thus http://biblehub.com/greek/1722.htm
Understood both from a spiritual and literal perspective....Christ dwells in us and we in Him.
You can't get any more of a real presence than that.
This is why the Scriptures admonish us not to grieve the Spirit, who also is in us.
I find no place in the NT where either Jesus or the Spirit ever leave the believer.
Christ is Christ. The Spirit is the Spirit.
One does not have a different Christ dwelling in them today and then the believer goes to a meeting tomorrow with other believers and a different form of Christ is there.
His presence is His presence.
Oh, no one doubts that.
But what in the world do you think Augustine meant when he said, "You were with me, but I was not with you"?