I have a ea81 subaru hatchback... Its idling all funky, i will set it to 700-800 it will stay there till i move then go back to 1000 i will set it again and do it all over again! But when I shut the thing off, and start it up it idles at like 400-500rpm! What could be the problem? I have checked the vacuum lines, changed oil & filter, changed wires & plugs, changed the air filter... And added some Magic Marvel oil. That helped the lifter tapping I also have fixed the exhaust system, it used to be held on by vice grips! Should I spray some carb cleaner in the thing? I think its a hitachi carb. Still has all of its emissions crap. I have also lowered the fuel mixture about 3 full turns untill it started to stumble then I backed off. I have had to drive it and tinker with the mixture and idle alot. It just always seems to want to go back to 900-1000rpm. I have to go threw emissions soon and I'm worried it won't pass idle emissions.

does it have a good return spring on the throttle?

Give your linkages a good spray down with carb cleaner, and then some good quality spray lube, then adjust your timing and idle speed. Might need to add a throttle return spring, it helped on my car.

Ok another thing I noticed is it idles down VERY slowly. Could this be the same problem?