Ok that makes sense. So in this example would the output from the MS mix with the factory ECU or is it split with this AEM extension harness ? I do know for a fact the plug is different for the 93-94 ECU so the harness wouldn't work. I guess what I need clarification on is whether the output signal from the factory ECU is severed for ignition and fuel or is it wired in conjunction with and the MS takes over output ? Because if I just need to clip the necessary harness wires coming from the MS that wouldn't be difficult. Also, I just looked on DIY, its been a while and they are now 559 assembled for the MS3. I have no experience with the MSPro but for what I would want in my 80 series I don't see any reason. i would really like to just get the truck to run super good on MS and then build me a turbo setup bump it up about 100hp. That has always been my major issue with the truck. I can accept low mpg if I can say I have some decent power. Plus I am a turbo guy and the big inline 6 is just begging for one.So even though you are using a standalone like the MS3. You would be wiring it in parallel to the stock ECU. The stock ECU stays in place and I like to use the AEM pigtail to plug in between the wiring harness and ECU so that I can do all my splicing and not hack any of the stock system.
AEM ECU Extension Harness Lexus LX450 4.5L | 4477ccL6 VIN:J [1FZFE] 96-97
**Might only work on 95-97 trucks, I am not sure**
You want to capture all of the sensors that you would need to run the engine stand alone and then output the proper signal back into the harness. SO things like cam and crank signal, throttle position, MAF signal, water temp, etc. You grab them and bring them into the MS3 and then have it output the ignition and injector outputs. This way you basically have full control of the engine but all of the other systems still get the signals they need to operate, i.e. the transmission, 4wd computer, etc.