i think i may be having the same issue as all of you, I've got a 97 impreza 5spd brighton wagon 1.8Lame, with 180xxxkm when i first got the car it ran rough and had a high idle (winter), had exhaust leaks etc etc i was getting p0141 (o2 sensor) and the code where idle is higher than expected (p0507?)
i cleaned the entire intake from the MAF to the TB, got a new exhaust and idle was a little more tame, (still cold weather)
then was getting horrid gas milage (7mpg) so i changed the WAY out of spec plugs, which fixed that.
-now that its warming up my car will start to limp once and a while on hot days (like described above)
-its weird tho, i went on a 80km trip with no issues and great driving (chilly spring day)
-then today (20 and sunny), stop and go traffic, taking small trips etc, on my way home it started limping right before i got home, could barely even hear my engine running while at a stoplight, so i plugged in my obd dongle and logged all codes for the next 3km i got home and screencapped the codes i got along the way and shut off my car, letting it sit for 5sec i turned it back on, and it was normal again.
i got these codes
p0141 (O2 sensor)
P0264 (Cylinder 2 Injector Circuit Low) <---- would explain the limping/shaking engine?
P0507 (Idle Air Control System RPM Higher Than Expected)
P1507 (Idle Control System Fault (Fail Safe Mode)
im going to try the neutral switch, aswell as checking the voltage on my injectors, dont feel like spending $200 on a iacv for a 1.8L would rather buy a whole new engine haha