[darkpuppet]

considering that NO is created under extreme temps, I find it hard to believe that it's because your engine is running cold.

maybe the CAT is running cold.. but definitely not the engine.

The O2 cheater shouldn't cause a fail (because the second O2 sensor is just to make sure the cat is working) -- however, it would be able to tell you if your cat is actually working if you had the 2nd O2 hooked up after the cat.

so what would cause you to run lean? I doubt it's the MAF/coils/etc... since the car, when tuned properly should automatically adjust for differences in the MAF. If you log your long term trim on the MAF, and it's a big number, then it could indicate that your MAF is not tuned properly.

If those values aren't too waay off, or even if they are, your O2 sensor (the 1st one) could be worn out, throwing off your learning function and causing hte car to the run lean.

See if your car is running lean (datalog your O2 as well as a wideband). if the wideband says you're lean an the stock O2 doesn't, then it's likely O2.

If the O2's agree, check your long term trims -- likely your MAF.

if both are OK.. check your EGR

if all those are ok, then it's likely your CAT isn't reaching operating temp (as that's the last possibility).

throttlebodies/plug wires/etc won't cause your car to run lean in closed loop, which is all they test for... so it's something that measures air or a/f, or a cold/innefective CAT or EGR.