You can deffinatly run a 2.5 on a 2.2 ECU. What year engine are you putting in the car? The MY98 2.5 ECU will plug right into the MY97 L ECU harrness. For that matter any DOHC 2.5 ECU will plug right in. So you could pick one of those up at Junk yard if your car is a newer SOHC 2.5 and it will still run the car fine. You may run into a slight problems with swapping over the sensors if the 2.5 is a SOHC engine. I don't believe it has a place on the intake manifold for the mounting of the Idle air control selniod and possibly other sensors. You might be able to swap manifolds between the two engines to solve this problem. If you choose to run it using the 2.2 ECU your best bet would be to add a fuel computer such as the HKS AFR or the Apexi AFC to assist in any differances of fuel maps. The MY97 2.2 engine ususally didn't have EGR so the wireing isn't there but the MY98 ECU is programed for an EGR so unless you wire up the EGR on the new 2.5 you will throw that code. If you have further questions feel free to PM or email me.