Subaru WRX to 914 transmission problems. The 914 transmission doesn’t have a VSS sensor or a neutral
switch. These items cause me idle and boost problems. I try to fix the idle problem, first I change my clutch/neutral to pulse the ECU when the clutch was depress. This had the effect of correcting the idle
problem ( before it took 3 seconds to return to idle) but the boost was still going crazy while in different gears ( 8 lbs to 15 lbs). I then check the VSS sensor and found that the VSS sensor wheel having too many pluses. I had 5 windows (5 IPRs) on my system with a Subaru Speedometer I was 17 MPH faster than the 914 speedometer. I then change the VSS sensor to 3 windows (3 IPRs) . It was like night and day
change. The idle problem went away, return to idle now, the boost was now inline with the gear I was in.
I still have a problem with the boost at times. I’m in the process of changing to a real neutral switch
and do more testing to see if this corrects boost problem. I will report back with the results when I
finish testing it.

It looks like you have to have a Neutral switch an a properly VSS sensor when using a 914 transmission.