During a debate with a Christian Scholar Imam Reza --peace be upon him-- asked the scholar if he knew for how many days Injil was lost after Jesus the Christ --peace be upon him-- and what is the reason behind the Christians going to church every sunday? The scholar answered maybe for a few days, as the answer to the first question, but had no answer for the second one. Then Imam explained that the Injil was lost after the Jesus's ascent, then two of the Christ's apostles said Injil is in our hearth and we will tell it to you, so come to the church every Sunday for us to inform you of its context, then they became 4 and people were going to church to learn about Injil, so that there are 4 gospels each having some differences compared to the three others. But anyway neither is the true one among them, nor are they intact, but all are corrupted. Shia Muslims believe the true one will be brought back to us with Imam Mahdi and Jesus --peace be upon them-- at the end (of the first part) of history! But among the gospels now available the one that goes well with the Islamic teachings is the Barnaba's Injil. According to Grand Ayatullah Bahjat, only four parts in this Injil contradicts with the Islamic Teachings! I have read parts of it. The main points of distinction between this and those most famous gospels are perhaps: Jesus is neither God nor His son but a distinguished creature of God, a prophet, and he repeatedly give glad tidings that a prophet would come after me who is known as Farghteliya (in Arabic it would be: Ahmad), which is the heavenly name of the holy prophet Muhammad, peace be upon him.
PS. I preferred to put this paragraph as a comment to the original question or to the answer given by @windmaker, but I am afraid my writings barely fit the size of a comment.