I have a 420 code for my cat. I cleared it several times but now it comes back the same day, and now I can notice the engine fluctuate at any speed when just to say on the pedal. My question is can I clean it? Like take it off and clean it out ? This morning I noticed the exhaust coming out around the front engine bay. Tune up done about 2yrs ago. 08 base 3.8. Thanks gang