Originally posted by Bob Blaylock:
My mechanic doesn't think a clogged cat would cause increased EGR flow, as I had theorized.
You may want to seek another mechanic, because he's wrong there. A clogged cat would definitely increase EGR flow. However, I think that the OBD-2 systems can detect a problem with the cat converters, and has a seperate code for it that would cause the CEL to come on. I'm not sure on this though. All I remember is my Ford dealer had no problem diagnosing my car as having plugged cats, and my CEL was on. But then again, my car lost all power above 3,000 RPM, so maybe that was a good clue 
'96 Contour SE, black / opal grey, MTX, every option, KKM intake, resonator removed, Flowmaster Series 40 DeltaFlow, GoodYear Eagle HP's, 115k miles, new paint 7/01. Driven cross-country 4 times.
'70 Corvette Stingray Coupe, Cortez Silver, 454 bored to 462, Muncie M21, too many mods to list, lots of fun. 335 rwhp / 365 rwtq
'02 Corvette Z06, Electron Blue / Black, every option. Stock for now...
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