bennyboy wrote:i have two large pipes running under the car and one smaller one. .
smaller one is probably the brake pipe, so I shouldn't get involved with that.
Not sure what you're actualy up to, but just copy the pipe layout on the non lambda car, the same as 90% of UK E30s.
If the ECU you end up using is from the lambda car, then plug the "electrical gadget" into the loom*, but don't connect the pipes. Just tuck the gadget away behind the suspension tower if it'll reach.
(* Important on M50 engined cars, but may not be needed with the less sophisticated M20 ECU. Don't know, TBH)