I have a 1991 fwd legacy with a motor in need of head gaskets. However I also have a great running 1.8 out of an old Impreza, with no issues. Would like to put the 1.8 into this legacy however the harnesses are different. What is the easiest way to get this done and is it going to be a noticeable difference in power?

It bolts right in. Bolt EJ22 intake and wiring harness to EJ18 and you're done.

 

If those early ej22 have knock sensor, remove it and thread it right into the ej18, the spot is there and threaded even though ej18's don't have one.

 

Same timing components between those engines - all the pulleys and belt and yensioner are identical.

 

Those ej22 head gaskets are super easy to replace if you want. Head bolts are external, resurface heads and new Subaru gaskets and you're done.

Hey thanks for the info I'll check back in with the results. Off to get started now. Thnx again

I am guessing you have a ton of miles on the 2.2 motor, less miles on the 1.8, so a good reason to swap.

good luck.  as to power - it's personal preference.  i'm never into speed, power, performance, etc.  i swapped an EJ18 into an originally equipped EJ25 1996 legacy sedan and it was underpowered but it performed just fine as a daily driver.  

in flat land it wasn't really noticeable, it was just a slow car but you can make up for it by just pounding the gas pedal if needed - those EJ18's can take RPM's all day long.

 

when i was driving 4 adults up steep mountain grades with oversized 16" wheels and tires - then it couldn't maintain 70 mph.