Your post touches on several issues.
First, communication. While I am not privy to your organizational chart, the fact that the General Manager is expressing such an interest in the audit report / rating would lead me to believe that he/she should have been involved, if only at a high level, throughout the audit and especially during the wrap-up phase. For anyone directly involved with the area under audit, there should never be any surprises presented in the final audit report. Both the findings and ratings should be discussed with management at the conclusion of the exam, and a draft report should be issued to management for their review prior to finalizing the report. These procedures will generally prevent surprises from happening.
Second, I would agree that if the audit report has a below satisfactory rating, the draft report distribution list should be expanded up the chain...depending upon the severity of the audit rating and noted deficiencies, even up to the President / CEO. Again, no surprises when the final report is issued.
In regards to changing the rating once the report is issued, my answer would be it depends. If the General Manager brings information to the table (things that existed or were in place during the audit, and maybe the line managers just didn't tell you about it) or brings a different perspective to you that results in your changing your mind, I don't see a problem with reissuing the audit report. Improved communication should make this unnecessary in the future.
If, on the other hand, things have changed since the audit, new controls or other types of corrective action, I think it would be appropriate to upgrade the area's rating (especially if the rating was less than satisfactory). This would not require you to reissue the audit report; the report as "accurate" as of the audit date. You could handle this with a memo or other documentation and just change the rating in your risk assessment and / or other summary documents. The main reason I think this would be appropriate is that auditing and the audit schedule should be flexible and based on risk; you need current, up to date risk assessments and ratings to do this.
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My opinions are just that...my opinions.