I have been reading about all this stuff for some time so i have a lot of the theory down and know about the systems, but i don't know anything about the installation. when you buy an aftermarket system, do you run it threw your stock wiring harness and add to it? I imagine thats what a 'piggyback' is. like an AFC or more. Whereas a stand alone has its own complete wiring harness with everything required to run the engine? I am eventually doing a 13bt first gen and am making a list of things i still need to get. and I need to make sure a turbo II harness doesn't need to be on it.

 

Most standalone like haltech or microtech come with their own harness to run completely alone. The new e6x from haltech can be run in full or piggyback mode, still need to use the harness for the e6x. Running with the stock harness just makes a mess of wires.



In your case, you don't need a TII harness. If you select a haltech, the harness that comes with it is all you need to get the engine going.



Some other ECU that use the stock harness are the PowerFC but you need to have a s5 or FD harness for those to work.

 

Plug n' play style ECU (Power FC, AEM) uses the stock harness and completely replaces the stock ECU



piggyback ECU's require the stock ECU to remain and splice into the stock harness. They do various different levels of engine control based on what you bought.



ECU's like Haltech, Microtech, Motec, etc. require their own harness to be installed, unless you decide to install it by attaching to the stock wires you want to use.



Long story short. Piggybacks are a waste of money. Plug and plays don't seem to be available for an engine that old. Buy a Haltech, Microtech, Motec $$$ for your engine and enjoy having completely new wiring for it.

 

plus being able to route it how everwhich you want

 

Cool. Thanx. Just wanted to make sure before i passed my chance up at a cheap s4 harness.