fuel pump mas combo

[jeffball610]

By MAS do you mean the mass airflow sensor? If so, yes you need it. Unless you have switched to a GM style MAF or some other form of air flow meter, you need it.

The MAS has nothing to do with the fuel pump. There is a relay from the ECU (I think) that tells the fuel pump to come on with the ignition. Fuel flow is metered by the fuel pressure regulator. The stock unit on the fuel rail should be good for basic startup and operation. A high flow adjustable unit is highly recommended when you step up to a higher flowing fuel pump. Base fuel pressure needs to be 38psi with no vacuum.

Fuel delivery is metered by the ECU by pulses to the fuel injectors. The fuel map inside the ECU is made up from air flow data and ignition timing at various RPMs. Base timing needs to be set at 5 degrees advanced for the timing tables to be correct. The fuel maps are adjusted in the ECU memory using the O2 sensor data versus the fule table. If there is a consistent variation of the base table over a couple drive cycles, then the table is updated with the current value in that part of the table.

Most of this info is available online when you search for things like setting up the Apexi SAFC and other piggy back tuning devices. I'm sure I made some mistakes in my info and generalized a little, but someone more knowledgeable than me will chime in to correct it.