The circuit is made with a differential pair Q1 and Q2 driven by a current source made of Q3 and Q4. The output stage consists of Q4 with Miller capacitor C1 for loop stability. The gain of the circuit can be adjusted by R10. Tune R10 all the way to zero ohms for a good MAF and when the MAF gets older (bad) increase R10. With the bad MAF I had, I had to set R10 to about 600 ohms (about half way) to get the reported airflow back on target.
Again all bipolar transistors. This to make sure that the circuit will work under any condition. Commercial available integrated circuits are normally not specified over the automotive temperature range. So they may deviate or even fail when temperatures are outside the specification.