I've got a 1998 sti wagon which had a vf23 on it and I replaced it with a vf28. Running on the stock ecu with everything stock apart from air filter,decat and 3" exhaust system.

With the research I did they are fairly similar and I should be o.k but I am going to get the a/f checked in a few days hopefully but in general are there any issues doing this on a stock car?

thanks