I assume you, too, believe that, unless the RCC has now stopped being Trinitarian. (Which some days appears likely since the RCC denies the work of the Holy Spirit in sanctification by turning it instead into some sort of ethereal nudging and holy post-it note suggestion box rather than a complete rebirth by the will and purpose of God.)
Faith does not save. Grace saves through faith.
Get the difference?
God has chosen faith in His Son to be the means by which He bestows His grace on whom He will. That faith acknowledges that Christ has paid for every one of the sins of His sheep, once for all time.
Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) And hath raised us up together, and made us sit together in heavenly places in Christ Jesus: That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus. For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them." -- Ephesians 2:4-9"But God, who is rich in mercy, for his great love wherewith he loved us,
Are you a modalist now?
If "faith in Christ alone" is faith in the Holy Spirit, then it would seem that Christ alone is the Holy Spirit.
The United Pentacostal Church awaits you.