so im going to do a swap soon,from a y7 to a y8 or the di5 anyway wat would happen if i put the ex or si ecu in first b4 the engine? just curious..

 

you would throw a check engine light.

 

any proformance changes?

 

Yea I'd say, probly run a tad rich and will have **** for low end being you will not be picking up a knock sensor which will pull timing to a certain extent being it will be in safe mode. You will be throwing CEL's for knock sensor, vtec, and IACV and it will affect everything from performance to gas milage.