If the Boost source is set to MAP then the target will be MAP. This is the most common option as MAP is what determines the torque (cylinder pressure) and also the factor that you need to consider against engine or driveline component strength.
The old two wire sensors are not good options. They were orignally designed in 1970 by VDO for use with their consumer level gauges, gauges in those days where very low resolution and were really just an indication what was going on.
The problem with them is they are very low resistance so they need a strong pull-up which consumes a lot of your available 5V output current, they are not linear, and their resistance curve varies significantly with the sensor temperature.
Have a look at Honeywell MIP series, decent sensors for about 50-60USD depending where you are.
