>.< whatever you do don't drive in the slightest bit hard. If you go over 3k rpm or get on boost you are very likely to pop your new motor until you get it tuned.
I think both verso and ecutek should be able to sort you out. Both are reflashes which use your original
ECU and just adjust some parameters to suit your modifications. Run a search on both of the above for more info.
Another thing I'd be interested in is how your heads work with the ej257. I thought 2l heads weren't compatible with 2.5l heads. I'm no expert though but worth checking out.