95 355 code check

Doing a friend a favor and looking at his new (1995) to him 355. Car has some issues but is a nice car overall. He came to me because I am a race mechanic and have a shop that works mostly on race cars and he trusts me not to take him to the cleaners. Biggest issue as I see it is the fact that it seems to be running very rich and rough at idel. Check engine light is on for the left bank and is on intermittent for the right bank. 60~ mph on the road it sounds great and runs smooth but low RPM it's rough and the pipes are black black black. So is this common? I don't have a code checker for it and I believe that it is OBDI. (pre 96) How do I read the codes?