A TII swap only becomes complicated when you choose to use a TII EM harness. With the NA harness, it's pretty simple.

Overall:
1) Swap in S5 TII ECU, MAP sensor, AFM, engine & transmission
2) Use a custom driveshaft (TII yoke & NA flange) or swap in TII driveshaft and rear end
3) Swap in a TII downpipe
4) Swap in TII fuel pump, FD pump, walbro etc...
5) Extend TPS wires
6) Plug 6PI connector into turbo duty solenoid (ECU pin 3R)
7) Cut VDI plug off and connect ECU-side wire to knock sensor (ECU pin 2M)
8) Get a TII hood and use the TMIC, or get a front mount
9) Get an aftermarket boost gauge

 

How is complicated? I have done many S4 and s5 swaps. The reason you would use a na harness is if you are on a short budget. I perfer t2 harnesses. I either repair them from scratch or buy new ones. Talk to hozzmanrx7 and he will agree how I do it. Maybe Im a perfectionist.
Thanks Robert

 

can you post pics of what to do to a s5 tii harness to adapt to s4 chassis? Im getting a j-spec s5 tii with ecu. The motor is from my brother's RHD. basically it's only wired to run,( ecu to engine) but all lights(dash and warning lights etc) are not working.