There are now direct fit swaps without wiring. you can technically run an EJ25 with the EJ18 ECU, but you get the lower redline and much less power than you should have. you also may have to run it on 92+ octane, because the 1.8 runs so much timing advance stock. The best way to do it is contact junkyards and recyclers about getting a complete front clip, which will include the engine, ECU, and all wiring, and swapping everything in. If you have the complete wiring harness, you can swap the entire car out. It's still a lot of labor, but you don't have to worry about tracing it out. You just pull out the old one, put in the new one, and plug it all in.

 

I have a 93 FWD L but i put a wrx turbo system on it and detonated, so i bought a 2.2 and just used the block and heads but i still use the EJ18 intake manifold and ECU, with 370cc injectors.