yeah i know i could do that easy, but i really want to run it on the series 5 ecu , its faster, little better AFM, better timing and better fuel mixture, all i want to know can it be done and if any one has done this before, i got both series 4 / 5 Factory Service Manuals so that will help a little

 

ALL s4 NA ECU's all swap over.
ALL s4 turbo ECU's swap over.
ALL s5 NA ECU's swap over.
ALL s5 turbo ECU's swap over.

The AFM can be done. wozzoom has done this on his s4. PM him for details.

 

I just recently learned that this is not true... The S4 'vert is NA but it cannot use a stock S4 NA ECU. (although I think you can go the other way...)

A/.

 

Is the ecu expensive to get?
cuz i might have to replace it in order to get it smogged

 

An easy way to remember which ECU's will work is, as long as the first two numbers match, then it'll work. For example:

My car(87TII) originally came with an N332, but an N333 and the N338 (NA vert ECU) will work the same.

 

how about replacing one? is it hard to and does it cost alot

 

It's not hard to change, get out your FSM and check it out.