My mate had a 95 wrx import, in which down the line he had gone for a fresh forged rebuild with a cdb and v4 heads and is a 2.1 now, after running the engine in, the car started giving problems, which was everything else but the engine, So he got rid of that and now my mate has bought another wagon which is on a MY99 uk , Now the problem is that we are about to put the forged engine in the MY99 and the inlet manifold from the MY99 does not align with the engine, The sensors are different on both the old and new inlet manifold, So now i was wondering would i be able to use the old inlet manifold from a 95 on a 99 as the sensors are differnet, and what will the ecu read. Also a MY97/98 inlet manifold will also fit on which looks the same as my99 and also allows front entry, but again would we have any issues with reading sensors from the ecu, Any help would be appreciated as this has bought a stop to the progress

 

Version 5/6 = 99-00
Version 1-4 93-98

The later manifold won't fit the early heads and vica versa, the best way out of this if you must keep this set up is to have the phase 2 manifold (99) modified to fit the early heads. You can also depending on how deep you want to get involved rewire the engine loom to suit, assuming you can configure the ecu accordingly, or swap the cylinder heads to suit.

 

I know you can modify phase 1, 1.5 manifolds for phase 2 fitment bu making them 15mm wider and using some adaptor plates (carl davey) but I've never seen phase 2 manifolds altered to fit the earlier heads.

I've done this the other way round and fitted a version 5 engine into a version 3 car using the version 5 manifold but retaining the version 3 loom.

The easiest way to do this is to keep the forged short engine and put on the earlier heads and manifold. They will pair uo with no problems. Although gasket thickness need to be right.