My friend has a 00 z28 that is for the most part stock besides a lid, headers, and a turbo400. He just bought the car w/ a diablo tune on it and it ran ok. He decided to uninstall the diablo to sell it and as soon as he did that the car ran terrible w/ a lean miss. The fuel trims were WAAAY off, like 50%. I went ahead and tuned it in sd mode and then dialed the maf in and now it runs good untill the upper rpms where it still goes close to 50% lean. The thing I noticed is that when he does more than 3x% TPS it seems that his o2 sensors read extremely lean, like in the 0-100mv range....
here is the current tune and a log, at the end of the log you can really see it...