Replaced the EGR, and many other parts, engine runs very rough, but HAS run well for short periods. Looking for how to access the "other" codes, Not the E 30 type ones, as we have done that. Plus, if there is a list or link to the procedure and what the normal parameters for a 4.9 in a '92 Deville, I'd appreciate that info as well. We have done SO much to this engine and are running out of ideas. Previously, it had run well on startup and crapped out when it got hot, but now it just runs rough at startup. This is a real quandry, we have NOT had this kind of trouble diagnosing and repairing any other vehicle before. Help please!