heres what it sounds like to me. you bought a used car with X mods on it.
You do not know what "tune" the car came with.
What you should have done:
1. talked to pervious owner
2. taken it to a shop and figured out what the tune was, if the previous owner didnt tell you, and make sure the car was tuned properly for the mods it had. DONE
what you should not have done, but did anyway:
1. start changing parts
2. not understanding what these parts do
3. not knowing what tune you are runing, and then going ahead anyway and changing parts.
now you are running a car with who knows what parts on who knows what tune. of course there are going to be problems and i wouldnt be suprised if they become catastrophic in the near future.
you need to get this car 100% stock with a 100% stock tune. give it a full look over, leakdown and compression check, get a clean bill of health and a fresh slate to work with, then start over.
Dude let me give you some advice. When buying a used car, ASK every single qustion you can possibly think of to the owner of the car you are about to buy. If they cant answer your questions, take the car to a professional who can (not a dealership if the car has been modified- we are talking an aftermarket subaru performance shop)
DO NOT under any circumstances start changing parts and or tunes without knowing what you are doing.
from the sounds of it you royally ****ed things up and should have left it as it was until you could do a little more research and figure out what you had to work with.
at this point i dont even know what to tell you cus i dont even know what youve done anymore at this point