Had codes for MAF sensor and O2 sensors. Replaced both of them and had the ecu reset. It is still stuck in some kind of limp mode. Before replacing, the car wouldn’t rev over 2000 rpm. Now it’s a little higher. It sputs and stutters when revving it out. I’m not sure what else to check next. Here’s my list:
Throttle position sensor $200
Spark plugs $5/ each x4
Coil packs $25/ each x4
Fuel injectors $100/ each x4
Map sensor $125
Ignition problems?
Vacuum leak?
Fuel injection problems?
Fuel pump or fuel filter or fuel controller?
Camshaft position sensor? $25
Crankshaft position sensor? $30

Other than that. My only guess is the clogged exhaust.

I doubt it's a plugged front cat, you'd be throwing P0420's and probably a bunch of other codes. Rear cat is a possibility. Two other suggestions

1) Does your scanner read the transmission? If not, visit the parts store, all their scanners do. Or get an ELM327 adaptor that's compatible with CVTz50. That app will give you engine codes, the ability to IAVL your new MAF, plus more info about your CVT than you knew existed.

2) Throwing parts at it obviously hasn't helped. You need a streaming diagnostic tool like Torque Pro or NDS-III, to look at things like your A/F Alpha (STFT), cam angles, TPS vs MAF, etc. Those apps will work using the same ELM327 adaptor as CVTz50 and help you figure out what's going on.

Why could the rear cat be a possibility and not the front one? Just curious.
I don’t have a scanner, I had it scanned previous to the problems, the reset the ecu myself to enact the new o2 sensors and MAF sensor, as recommended. It could still have codes.
The new sensors did help some. As my fuel mileage returned to normal. Went from 90 miles left on my tank to 140 miles left after the o2 sensors were replaced. After the MAF it went from limp mode at 2200rpm to 3000-3200rpm.

The car is a 2017, with only 84,000 miles, if that helps.

I have no issues shifting in sports mode, driving in limp mode in normal drive. Reverse is fine. I don’t have any reason to suggest it’s the transmission. To me it feels, and from what I have read, some sort of fuel problem. Which is why my list of repairs and diagnoses are what they are.

The rear cat isn't monitored, the front cat is. Like I said, you'd get codes from the front one.

The MAF won't calibrate with a "reset", there's a special procedure for it called Idle Air Volume Learn (IAVL). If you didn't do IAVL on the new MAF, that could be your issue all by itself. IAVL matches up the MAF readings with TPS angles in the ECM's memory. Since QR25 ECM's are totally dependent on an accurate MAF, an uncalibrated one is perfectly capable of causing mayhem with no codes at all. I've seen pieces of lint or butterfly wings literally render QR's undriveable.

If you have a 'Droid phone, the apps and adaptor I suggested will cost you a grand total of about $25. Get a VeePeak VP11 adaptor, it's the cheapest one that works right with CVTz50 and they're $18 all over eBay. If it's Apple then there are other packages like Blue Driver, but my understanding is they aren't so good with the CVT. I'm a 'Droid guy, so others can advise you on that count.

Okay all of that makes sense. Unfortunately I have an apple phone and computer. What is a proper recalibration for the MAF then?
I’m mechanically inclined some what, not so much with transmissions, engine internals, or reading charts and graphs pulled from those things.
I’m also living paycheck to paycheck, (inflation, life sucks, debt, etc.) so I’ve just been doing and buying what I can. Not saying I’m poor but not saying I’m well off lol. But being down a car has sucked!

There's a manual procedure for IAVL, although it's a little stilted to perform on an I-Key vehicle. See page EC-187 here, it's for a '16 but your '17 will be identical:
https://www.nicoclub.com/service-manual ... 6%2FEC.pdf

Anybody have some help for this man for an Apple package that won't break the bank?

I appreciate your help and advice, thank you!

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I am having the same problem were you able to get it figured out?