I have a similar problem got my car little over a week ago now im experiencing all these problems....its a 05 ssl with 27k miles on it...the second day i had it the SES light went on...checked it out today found out it was "02 sensor circuit malfunction bank 1 sensor 2". Ok-no big deal-Will take it back to mitsubishi and get it fixed. But then it seemed like today everything started to go wrong:

-Started experiencing a loud noise when boosting sounds like its coming from the front right side-sounds real nice-but i never heard it before or when i first got the car.
-second thing is the rotors-wheel is shaking when driving on the highway and brakes sqeak when slowly coming to a stop.
-new problem today i heard was a noise as i slowed down sounds like something wrong with the brakes, i have no clue to what it could be though.
-also notice idle shaking at start up and ticking from the left side of the engine bay-heard this was normal but it still pisses me off.
-on top of all this im getting annoying *** rattles from all over but today was a bad one coming from the top of the steering well.

WTF IS WRONG WITH MY CAR!!!!!????? I am not pleased with any of these things and i hate having little things like this that i dont know about that **** me off..HELP

 

previous owner probably warped the brakes or changed pads thats why there is some sound while braking and shaking at highways. my car started rattling 2 months i got the car... get use it usually it goes away so wait a few days to see what happens.

my engine ticked before when engine was cold... changed new oil and ticking sound went away. good luck

 

Looks like you bought someone's car they put back to stock. You should be able to straighten things out pretty quick. Doesn't sound like anything too major.

1. If you have a modified exhaust, you'll get the o2 sensor code - P0420 I believe. You can get the electrical Perrin o2 simulator or a cheap 02 sensor spacer. This should fix up any o2 issues you have.
2. What kind of intake do you have? Stock? Drop-in? Open air? The latter will result in loud spooling more than the former intakes. If this is the case, then it's normal and there's nothing to worry about. However, if it's a brand new noise, then you need to check for a boost leak. Make sure all couplings are on and the clamps are all tight. The stock clamps suck too, so you might want to upgrade those.
3. 27k miles on the original rotors = time for new rotors. Try picking up some good slotted (not drilled) rotors and pads. Seat them correctly and no more shake or squeal. I've seen some nice group buys on these things on evom in the past. This could also be the source of your new problem.
4. Your idle shouldn't be off at all unless you have a vta BOV or a crappy tune. If you're not running the stock BOV, then see if you can find one and give it a try. You should be able to pick up a stock 03-05 plastic BOV for free from someone on evom. You could also try the JDM or 06 BOV.
5. Evo = rattles. Not much you can do about them unless you're willing to start taking things apart and searching. I've had a couple I was able to locate and fix, but I'm still working on one more that I can't seem to find.

So there you go - I doubt there is really anything seriously wrong with your car. Let us know if you're having any success with getting things worked out.

 

so let me get this straight -

You bought the car used and had a check engine light come up....the bank 1 O2 sensor malfunction which means the sensor probably isnt heating up like it should. So clear the light, and see if it comes back. If it does then replace the O2 sensor. Dont know why your car is shaking & making noises while you brake unless you have warped rotors or mitsu didnt tighten the lugs all the way; if they even took off the wheel. the ticking is normal and so are the rattles, sorry....welcome to the world of evo's

 

hahahaha..you beat me to it SP00LIN...lol

 

hey guys thanks for the posts...
--first of all i found out my car had HKS 272 cams installed-so that explains the minor shaking at idle.
--brought my car into the dealership yesterday...called them today and they said they ordered the part for the o2 sensor...btw the code was po136, so that should be soon taken care of.
--however i told them about the rotors and they told me "they couldnt drive the car over 70 mph in the area they were". - A bull**** excuse.
--As for the noise, I am thinking its the turbo fighting against the stock exhaust--previous owner had put an exhaust on and taken it off like you mentioned.

Anyway, like you said spoolin, nothing major. Thanks for the responses and let me know what you think from here.