For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Full disclosure, I'm not Pentecostal. But I would suspect it's because they use the events at and surrounding Pentecost for support of their non-traditional beliefs which focus around speaking in tongues.
The Gospel was established in the book of the Acts of the Apostles and Apostle Paul said later as follows..... 6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: 7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. 8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. 9 As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.
The Holy Bible : King James Version. 1995 (electronic ed. Of the 1769 edition of the 1611 Authorized Version.) (Ga 1:6-9). Bellingham WA: Logos Research Systems, Inc.
I'm not exactly sure what you're trying to say here. The Gospel is Christ crucified. For all those that believe it, they are forgiven of their sins, they are brought from death to life, and are adopted as heirs. We become righteous because Christ is our righteousness. Paul declares in Ephesians 1 that all Christians are sealed with the Holy Spirit.
Problems arise when everyone seeks the least path of resistance in any thing we do, let's look for the easy way, the feel good scriptures and base our salvation off those...simply read the bible! The book of Acts lays the foundation for our salvation, once we have followed the plan that was given by the Acts of the apostles, now we can have Grace and the mercies of Jesus, our God and savior . Even Paul tells us in Rom 6:17 But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you. The only doctrine that was delivered was in the book of Acts. Open your hearts and read your bible and let God lead your sincere heart to him