sooo i changed out my iacv valve on my 2000 civic si and it made a difference and all but i took the car to get scanned today and it pulled out 3 codes
knock sensor
catalytic converter
and my idle air control valve
okay reset the ecu for the iacv valve it was running pretty good till 3 hours later i started it up... sooo i guess the knock sensor next and the cat
should i go test pipe or not my car has the apexi muffler on it and that is pretty loud i am not trying to get tooo loud...

 

Definately get that knock sensor fixed.

 

Yes, fix the KS. The code is thrown only after the cooling fan has cycled at least once and when the engine is over 3000 or 3500 rpms. You can get the light to throw by simply letting the fan cycle then rev the engine and hold it around 4k. Light should come on. Replace the sensor and repeat this process and the light should stay off.

You obviously need to fix everything to turn the light off permanently. If you just do a test pipe, you'll have to get a rear O2 simulator or do the oil fouler trick on the rear O2 so it won't throw the catalyst efficiency code again.

 

this is very expensive man
would u think if i take it out and plug it back in it would be alright???