I have an 03 impreza wrx and the crank went so I rebuilt the engine in it and removed Heads, Manifolds etc from the ej20 block and put them on an ej25 block.
I cleaned everything I could clean twice and used a new oil pump, oil modine etc. Now the engine is back in and running I have run in to a few problems it ticks over around 2000rpm and the engine shakes alot. If I drive the car it is a bit jerky up to about 3000rpm where it then seems fine.
I pluged a computer in to it and it came up camshaft sensor so i changed it and no joy it still runs the same and with the computer pluged in it still comes up camshaft sensor. I have checked all the wiring, checked for loose pipes and air leaks.

Any help on this problem would be much appreciated

 

check the left banks cam inlet wheel has all the teeth on the back of it that the sensor reads....