Is there a remnant of Jewish believers in the present age of grace?
Yes. Paul writes that in this present age of grace, which is predominantly Gentile with some Jewish exceptions, there is a remnant of Jews who have become believers of the gospel of grace. They are a remnant according to the election of grace, not of law or Judaism.
Les teaches a doctrine of the remnant running all the way through Scripture: God has always kept a remnant. He points to Christ's earthly ministry and the broad way versus the narrow way—the mass of humanity goes the broad way, but the remnant takes the narrow way. Then Paul says that with regard to the Jew in this age of grace, which is predominantly Gentile with only some Jewish exceptions, even so at this present time there is a remnant—a small percentage of Jews who have become believers of the gospel of grace. This remnant is according to the election of grace, not of law or Judaism. Les also mentions reading testimonies of Jews who became believers of this grace gospel from many backgrounds, and how God worked in their lives until they could believe Jesus of Nazareth was the Messiah who died for their sins. They are a remnant, very few can believe it, but they are there, just as Elijah was shown 7,000 who had not fallen to idolatry.
Even so then at this present time also there is a remnant according to the election of grace.