Brummie,
Why would Jesus promise to be where 2 or 3 are gathered in his name if he is omnipresent? To be omnipresent, he would also be where 2 or 3 are NOT gathered in his name and where 2 or 3 hate his name. So, what would be the point of his promise?
Hebrews 9:24 says: "Christ did not enter a holy place made with hands, a mere copy of the true one, but into heaven itself, now to appear in the presence of God for us." Acts 3:20, 21 says that God will "send Jesus, the Christ appointed for you, whom heaven must receive until the period of restoration of all things about which God spoke by the mouth of His holy prophets from ancient time." And an angel told the apostles: "This Jesus, who has been taken up from you into heaven, will come in just the same way as you have watched Him go into heaven." (Acts 1:11)
These texts establish that (1) Christ is in heaven, not omnipresent upon the earth, (2) he will remain in heaven until the coming restoration of the earth, and (3) he will return to the earth in the same way he was taken up from it.
True, Jesus said he would be "with" his disciples until the end of the present age. (Matthew 28:20) But that is not due to his being omnipresent. Instead, it's in the way he specified. "Jesus answered and said to him, 'If anyone loves me, he will keep my word; and my Father will love him, and we will come to him and make our abode with him.'" (John 14:23) That was the assurance he gave to the apostle Paul when he told him, "I am with you, and no man will attack you in order to harm you." (Acts 18:10)
If Christ were omnipresent, his abode would be with everybody, not just those who keep his word. According to the context of John 14:23, Christ makes his home with his disciples by means of the Holy Spirit. This presence is very real. Its operation can be felt. The Spirit will convict of sin, lead to daily repentance, impart assurance of salvation, bestow the peace of God that passes all understanding, admonish, and comfort - all of this in connection with the Scriptures. It is in that way that Christ has promised to manifest himself to the disciples, but not to the world. See John 14:15-22.
fjtoth