never thought of that because the s4 is mechanical versus the electric S5 right? This one is in working order so I suppose just leaving the S5 hanging at the harness wouldn't be a bad option.
Both engines are capable of pretty much the same power. The advantages of going with the S5 is mainly in the stock turbo.(wastegate is larger for boost creep and the they ditched the stupid twinscroll) The turbo on the motor I'm selling has the wastegate ported and the flapper for the twin scroll is locked in open position BTW. Do your research but hopefully you pick up my motor. Either way you'll be getting a good one because Japan2La sales great motors.
Part of my problem too is regardless I need a new wiring harness. My car sat for years before I got it from the PO. In that time, critters of some type managed to get and chew through the harness in at least 3 different places (that's is from what I can see from the engine bay, it may be more. So to me I will need a harness regardless of which way I go.