http://cgi.ebay.co.uk/OE-Lambda-Sensor-For...212121001r22143 .Front sensorSame number as import car parts £119 that same company's has the rear sensor for £109
Going by you and your subaru impreza book by Chris Rees ppp from 1996 to 1998 238bhp at 5600rpm 240lbt at 2400rpm .There is no mention of ppp before this date i mention above
Litchfield MK2 type 25 is running a Cosworth engine
http://www.type-25.co.uk/engine_engine.asp
I would go for a litchfield type 25 with one of the new turbo dynamics twin scroll turbo's fitted in a Jdm hatch
See with your green cotton panel filter .You need to cut of the rubber lugs of the under side of the rubber lip on the air filter or you won't get the air box shut may be you know this all ready
The KLC39 and KLC38 are the same droplink just different fittings .The klc39 have all 10mm bolts four spacers for newage KLC38 have 2 10mm bolts 2 spacers to fit that size and i think the other two bolts are 8mm with machined spacers for classic