Ok so here is the good news!!!
This weekend I took off the throttle body, cleaned it and also took of the IAC valve wich seemed to be quite dirty... I noticed it has an adjustment similar to the TPS sensor, but I left it on the same position.... I also noticed one wire under the TB that was supposed to go to ground... and was unplugged, so i plugged it back and sealed it with black tape.
Put everything back together and the misfiring is gone
the engine runs smooth, now the only problem is that is idling from 2,000 rpms while cold and 1,500 while hot.... Im thinking it could be the TPS sensor adjustment so im going to try to adjust it today.
I think the failure was all in that disconnected ground wire... wich by the way it looked like some custom installation, maybe something related with the transmission swap or the ECUTune... I believe the tranny swap sounds more logic....
Well. I really apreciate all your help
I love my SVX again
And now im going to start getting more mods to make it perfect.
I'll let you know how the idling problem went.
Oh and by the way. I found this Shop called FAT here in Phoenix, he seems to be a subaru speciallist and he told me he know a lot about SVX's