I have an ITS 2nd gen racecar with a S4 ECU. I would like to convert the electronics to an S5 ecu, maf and injectors to be able to plug and play a spare S5 motor that I am rebuilding. As a racecar all the emissions have been removed so the harness is down to the maf, injectors, cas and tps.

Can I simply bolt in the S5 ECU and use the S5 harness?

 

Others will have to confirm, but I think you need the S5 OMP.

 

Not a problem, I have the S5 OMP.