Sorry but it isn't referring to what is imputed in reference to God and his knowledge of sin but rather in reference to men and what they have knowledge of and therefore before God they are guilty even if they are not fully aware of exactly why.The penalty for the guilt of personal sin is the second death; physical death is the inheritance passed on from the results of Adam's sin. I am not burdened with the guilt of my forefather's sinful acts, but the effects of those acts are endured by all who have followed after. Paul's covetous acts, prior to understanding the commandment, " You shall not covet!", were indeed sinful, but Paul is not held as guilty until he has become cognitively conscious of what coveting is and the prohibition of it!
They however will know enough that there is something wrong in their conscience albeit they will not know exactly why but that is still enough knowledge to cause them to question themselves and where they stand with God.
Furthermore, Paul in Romans 7 is not speaking of himself before he was saved but rather after he was saved and the chapter is about the tension that exists with believers between walking in God's grace and walking under the law being they know the law.
For although we are saved by grace and walk in the Spirit, there is always a tension in moments of weakness that wants to pull them back walking under the law instead of the Spirit and Paul is showing what will happen when this occurs.
What proves this, is his words "for I know that in me, that is, in my flesh dwells no good thing" for if Paul were not yet a Christian with a new heart, he would never have backed up after saying "for I know that in me" with "that is, in my flesh" for the problem of sin would have also been in his heart and not only his flesh.
Very clearly therefore Paul in Romans 7, is speaking of the problem that will occur for every believer, that while we desire to walk in God's grace by the Spirit, we will drift back in moments of the weakness of our faith, to attempting to obey God by the law and which will prove to be totally fruitless and therefore drive us back to walking in the Spirit again.
What Paul is referring to at the end of chapter 7 when he says, "therefore with my mind, I myself serve the law of God but with my flesh the law of sin" is how it is when believers desiring desiring to obey God with their mind, end up serving sin because they are caught in a moment of weakness with their faith attempting to obey God by the law.
No one has perfect faith to walk by God's grace and in the Spirit all the time without failure, but being a true Christian has a changed heart and will always want to please God, in those moments of weakness in their faith, they will occasionally attempt to obey God by the law and the failure because of this will turn them back to grace.
This is what Paul is speaking of in Romans 7 and it is a normal occurrence with believers and will happen also but as they grow in God's grace and in their faith and in their learning by faith to walk in the Spirit, they will have more and more success over it.