DOH! I had a brain fart. I typically disable long-term fuel correction during my testing, so the +/- 25-30% range of authority that I've observed is strictly within the short-term fuel trim. If you add the long-term fuel trim range of authority, I can see how the vehicle can be + 50%. Still, that is a pretty serious error. I'd suspect a serious vacuum leak OR maybe even an exhaust leak (O2 that didn't burn coming through the engine looks the same as O2 that can in after the engine).

1999 Contour SE Sport MTX75 T-Red/Grey
Audio: Pioneer DEH-7400MP (MP3 CD), Pioneer TS-A6857 front & rear, PPI PCX-250, Infinity Perfect 10.1
Other: cup holders, cargo net, Blizzaks, Potenza RE950s