Monkman08

Correct. You might run into issues with the ECU though. The earlier ECUS were able to handle this swap but im not so sure about a newer one

Couldn't i just get an ej25 ECU from the wreckers if the one i have isn't self learning? 

Using the 2.5 heads

It sounds too good to be true haha. So many people reckon otherwise. The engines are basically the same apart from the bore size. Amiright? If you or know someone who has done this. i guess ill just risk not getting a refund on the engine. Id much rather the EJ25 over the EJ20. Thanks for your help BTW. much appreciated.  

Manifold should just drop on

The only thing you need to be careful with is cam trigger wheels and things like that

I can't see any of that stuff being different

Without replacing or using the existing heads?

Ok. The problem i have is a pretty long one. I cooked the ej20. Kinda. Blew the gaskets and the heads will probably need to be machined.

To replace the gaskets and machine the heads. the cost was close to 2.5k. The engine had just done over 200k. I thought it would be heaps easier. if i could get a newish engine. Some bad advice given to me. apparently you can't just swap an ej20 with an ej25 very simply. (Without changing the ECU and Loom). I managed to pickup an EJ25 with only 30k's on the clock. for $2000.

Ive heard from a subaru guru that just replacing the intake manifold should do the trick. I just don't know if the EJ20 manifold would fit on to the ej25 block. And i can't test fit it without voiding the new engine warranty/ ability to a refund.