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...

When you talk about rescaling the MAF, it sounds like you've got some back ground in the domestic world. Unlike that world, we don't have access to injector data in order to make the kind of changes needed to rescale a table the way the domestic world does.

If you have a 3" intake then you need to have a tune with the right MAF calibration, otherwise the symptoms are exactly what you're experiencing. It's not a MAF problem, seems like a calibration problem. Ok cool. Thx for the reply and putting me out of my agony. I will check the site for a tun...

Are you running a spacer in the rear O2? This will help make the code less temperamental. Aftermarket Cats are more sensitive when it comes to setting Cat codes. Sometimes there are some fueling tweaks that need to be made in order to keep the Cat warmed up enough to stay above the code threshold. W...

Need a copy of the tune and possibly a log to look at.. It might be as simple as cutting out a few cells where you've got the timing reduced for the crackle..

Can you post the logs.. Have you gone through some of the guides to understand what you need to log.. can you also post the tune you are working with.. I personally have little to zero trust in AI looking over a log.. There are things going on such as possible swings in your AFR that is likely norma...

You're also getting quit a bit of knock which.. That's the ECU freaking out when approaching the boost limits (according to the sensor at least)... As for the clogged cat/exhaust... usually the turbo will not build boost in such cases, but in his case the boost jumps a lot while the airflow doesn't...