Being that the Arduino is trying to replicate the OE MAF signal, it seems like KFKHFM would apply, though it’s ability to make up for the potential inadequacies/discrepancies of the Arduino remains to be determined.

That being said, agreed the rs6 method is much cleaner, thanks for pointing this out and also agree the barrier to entry with Arduino is much lower (I will go learn how to implement the routine in the ecu). The trivial algorithm that was pointed out is exactly what is bing used (nothing fancy), just outside of the ECU in a separate controller.

As was pointed out, the loop rate of the Arduino vs what the ECU is expecting is a point of risk along with how fast the Arduino can respond to changes in airflow.

prj, why not suggest digging the MAFs altogether for your MAP based load conversion?

For this you will need to program atmega328p(most arduino boards use it)  in C, without any libary.  It will take you more time to learn all that than ASM in C167
And as other suggest, stock ECU will be more safe to use, and it will be far more better.
I am using atmega328 for years pushing it to limits, I know it can do this task to work without problem, but I also suggest do it with stock ECU

Thanks everyone for the valuable input and pardon my ineptitude on the matter. This sets up the 2.7t Boxster for success and I appreciate it.

The length of the suction path, from the air flow meter to the turbine impeller, is 1.5 meters.
Y-pipe is asymmetric at the inlet (near the flow meter) and with a large angle of attack of the air flow.
What "linearity" are we talking about? This is pure savings and implementation on one flow meter!
In terms of gas dynamics, a design with a crooked Y-pipe is an engineer's nightmare. It is near the measuring zone of the flow meter that the swirling of the intake air flow occurs, distorting the measured data!

The desire and the idea are clear and real.
Personally, I implemented a signal adder for two flowmeters for atmega 328, two 12-bit spi ADCs and one 12-bit spi DAC. Based on two Bosch flowmeters
0280217814 with a limit of 1560 kg/h and corresponding original linearization curves interpolated to 12 bit resolution.
After working with the code, we got a sampling time of 20 kHz at a resolution of 12 bits.
The addition of values ​​from two flowmeter signals is performed correctly and coincides with the mathematically added values.
The naturally resulting linearization graph(MLHFM) is created mathematically as a sum and put in me7.1.

The official Bosch information about HFM5 indicates the following time parameters for converting air flow into voltage:
1) T1 = 15 ms (In case of sudden increase of the air-mass flow from 10 kg · h–1 auf 0,7 Qm nominal, time required to reach
63% of the final value of the air-mass signal.)
2) T2 = 30 ms ( Period of time in case of a throughflow jump of the air mass | ∆ m/m | ≤ 5%.)
With a conversion time of 15ms, we obtain the maximum frequency of the air mass meter signal change equal to 66.6666 hertz
The available 20kHz ADC/DAC sampling rate is more than sufficient to respond quickly to changing flowmeter signals.

It is important to pay attention to the reference signals Vref, which are twisted into one point by the author of the topic ...)