If you are starting from scratch that means you have your stock tune from the ECU to work from. Can you post it.

Can you post your tune.

How many miles on the car? You're MAF signal is very messy.. Do you have an intake on the car or is it stock? MAP signal is also a bit messy.. Sometimes this can indicate a miss fire. You're also knocking right from the get go.. Can you add control module voltage, and Fuel trims to the log.. You can...

Finally after smoke leak test, the oil breather hose was leaking. This propably explains the high (3.2 g/s maf reading) at idle and negative ltfts (-12%). After fixing this both stft and ltft became almost 0 and maf 2.5-2.7 g/s. Tomorrow will test it and upload a new log with versatuner. Crazycanad...

I prefer FORScan for data logging. You don't need CAT temp. Include EQ_RAT11_DSD to your logs and BAT... How is your waste plumbed? Factory Bleed set up?? My concern with the log is your STFTs are climbing to +25...

can you post the tune file?

The rear 02 sensor is used to monitor the cat efficiency though so obviously and engine running at say 12:1 is not going to be producing the correct input to the cat therefor the output will be wrong and the rear 02 sensor will allow the ecu to adjust for that. Pretty standard practice on all gm, f...

Have you built in some sort of air "straightner" or MAF screen to smooth out turbulent air across the MAF sensor? This would have been built into the stock maf housing. It's also designed into any good aftermarket MAF housing. It's needed in order to get a consistent reading from the MAF. ...

Can you post pictures of the intake and MAF housing? It sounds like you've got a stock housing on a bigger filter/turbo inlet pipe..

Yes air filters can be a restriction, but I don't think that's what you are seeing. An air filter is going to effect the path the air takes as it flows into the intake tube and across the MAF sensor. This will effect how much air the sensor is sampling which screws up it's calibration.

One other thing I forgot to mention. Just cause the code is setting doesn't mean the Cat is bad. It doesn't mean it's a performance problem, plugged or anything to worry about. It just means it's not passing a "subjective" ecu test. It's saying your car is putting out more than allowable e...