cliffh

I just put a JDM Phase 1 2.5 into my 98 Outback to replace the Phase 1 EJ25 that was in there. The JDM engine had the egr port drilled so I transferred my intake manifold over from my USDM engine and hooked everything up. The problem I'm having is when I go to fire it up, it will run for a few seconds and die. I gave it a bit of throttle a couple times, when I did this the car would run a bit longer, I would get clouds of white smoke out the tail pipe, the car would stutter, backfire (exhaust smoke through the air intake)- then die. I changed the timing belt on the JDM before installing it. I read a ton of posts on this board as well as the Hayne manual to make sure I was doing it correctly. When I changed the timing belt, I rotated the engine until all the time marks were lined up according to the diagram in the Hayne manual. For good measure I took a silver sharpie and marked the position of the crank shaft and the cam sprockets in a couple different places. I'm confident that the crank shaft and cam shafts are in the same place they where in when the old belt was installed. I counted the teeth on the timing belt between the timing marks as well, it all looks good. I rotated the engine by hand several timing to listen for valve interference and heard nothing. The problem I'm having sure makes me think the timing is off, however I've pulled the timing belt cover off and re-double checked everything and it all looks good. Is there anything related to the sensors, vacuum lines etc. that may be causing this type of problem? Any ideas? Any help would be greatly appreciated!