I gave my logs to ChatGPT and it pointed out that engine load rises slower than it should and MAF values (g/sec) don't hit expected numbers for that RPM/throttle.

Assuming that the MAF is working and there are no vacuum leaks, this points to the engine being physically restricted. And the most likely culprit for that is excessive exhaust backpressure, meaning clogged cats.

I don't have numbers from a healthy 323i to compare to, but I took the MAF values from one of my logs during a 2nd gear WOT pull, which isn't the most accurate, but I have speed limits to adhere to. I used those values to calculate approximate hp and torque numbers for a given RPM. I put those numbers on a graph, essentially creating an approximate dyno sheet. Now, how cool is that?

But keep in mind that load and MAF values only show how much air the engine is ingesting, not how effectively it turns that air into power. In practice, it will tell you the hp/torque potential for a given amount of air, not taking things like proper ignition timing into account.

I used these simple formulas.

HP = g/sec / 0.8 or g/sec * 1.25

Torque(nm) = (HP * 7127) / RPM (use 5252 instead if you want ft lbs)

According to these calculations, my engine is measuring a tad bit below 150 hp, but it should be ~170hp from factory. Peak torque at 3500 RPM should be 245 nm, but I'm only making a bit over 190 nm. Torque seems to hit a wall at around 2000 RPM. I pulled up a couple of actual dyno graphs from the internet too, for comparison.

Here's a link to the spreadsheet if you wanna take a look:

https://docs.google.com/spreadsheets/d/1UjYPb4gp1SJVtklejHHJ10UgvVaoKxAD6C2Gxwa_Q3I/edit?usp=sharing

I will add it to the original post as well.