Ok, few things:

First: I've got my engine (S5 TII), but no wiring harness or ECU. I know that I can use N370, N374, and N380 ECUs from reading stuff, but what wiring harnesses can I use? I've heard that you can use the harness from an NA, but what about S4 wiring harnesses?

Second: probably a stupid question, but is there any reason I can't have my fuel pump on whenever the engine is running, do I need to put in the stupid fuel pump relay?

I think thats it... thanks in advance for the help.

 

first question: don't use an s4 harness. they have a different TPS, OMP, and a bunch of other stuff. Plus the s5 has an additional ECU plug.

second question: hell you could keep a jumper in the fuel pump check connector and have the pump running any time you have the key in, but that increases the risk of a fire in case of an accident.