I just have a few questions. I have a 88 fc vert with a s5 swap in it running off an s4 ecu. There are supra injectorsin there and a 3" cat-back system. This car will primarily be my DD untill I get another vehicle to drive.


Is there a difference between the two ecu's or do I need the s5 ecu?

Would I be better off with factory injectors?

Would I be better off going with a facotory or smaller sized cat-back system?

With stock suspension, am I good to use loweing springs?

 

There is a difference. Perhaps this link will help you better understand what you're trying to take on. Rotary Resurrection: Swapping an 89-91 (S5) Engine into an 86-88 (S4) Car

Yes.

You should be fine.

Yes. It all depends which springs you choose along with the wheels and tires you're using.


There's plenty of great information in this particular section -> 2nd Generation Specific (1986-1992)