Yellow wire goes direct from the tacho interface, to the connector at the end of the coil pack assembly.
Here is the noise filter/capacitor setup, resting where it has always been, and should be located on most 4g6X motors. You need this piece, it is there for a reason.
This is the fanout sheet for the 4g61t, 90 DSM coil wiring.
Compare this to the wires you see in the first pic. It shows a tap-in to the white wire on the fanout sheet, that says tach.
Now Mitsu sometimes got things a little wonky, when they translated and had it drawn up. Does this mean tach filter or tachometer ?
That wire is spliced into (also a ground braid to keep unwanted RFI from being inducted into the wiring), which is also another white wire and that leads up to pin 109, fuel pump control. I "assume" this is the spark induced signal, and either the ECU or the MPI relay keeps the fuel pump running until the ignition feed is interrupted.
Big picture, I know. Use a "Control" + "-" key combo, and it may shrink the picture in your browser.
http://www.lilevo.com/mirage/ECU%20edit ... mplete.jpg
Section 8 Page 26 of this 90 Talon Technical Manual shows the 90 wiring yet again:
90 TALON Technical Manual
Section 8 Page 27 shows more wiring at the ECU, proving pin 109 is the tachometer signal spliced into the ECU and out to the tachometer.
Your coil pack setup must have the capacitor wired in, and be functional. This capacitor is above and beyond the one sitting on the top of the intake manifold.
For reference, the JDM Cyclone dual runner manifold wiring had a capacitor in the same location at the top corner of the manifold where it takes a turn down to the injector wiring.
BINGO!!!!
This next picture shows the transistor inline with the white wire as it heads up to the tachometer assembly:
Click me for HotRodCoffeeShop's DSM wiring for Dummies, 90 DSM wiring fanout
Pic of my capacitor installed on the 90 coil assembly bracket.
Pics of the inline filter.
^^^ Looks like the two wire inline filter is required. The one wire option strikes me as a simple noise filter off a coil pack, or a 4g15. Can't quite place it ....