So then your "belief is faith" argument falls by the way side. There can be a difference between belief and faith. That accounts for the fact that the everyone (unregenerate people included) has the capacity to believe as Jesus demonstrated in Mark 1:15.
I never said that this is a passage for grace through faith. What Romans 2:15 does get across is that the unregenerate man is not at a total loss for believing God. He does have his conscience that can guide him towards choosing to follow God.
Stop calling the Bible fiction.
If you would just look 2 verses before the passages you recommended (Rom 8:7,8), you would have seen that I was right when I said that "those are people who live according to the flesh":
5 Those who live according to the flesh have their minds set on what the flesh desires; but those who live in accordance with the Spirit have their minds set on what the Spirit desires.
6 The mind governed by the flesh is death, but the mind governed by the Spirit is life and peace.
7 The mind governed by the flesh is hostile to God; it does not submit to God’s law, nor can it do so.
8 Those who are in the realm of the flesh cannot please God.
My point still stands. Those are people who live according to the flesh. That means that they have seared their conscience and tossed out whatever good God has gifted to them. They were gifted with the tools to believe God (their God-given minds, for one) but they squandered them.