Well, the way they work is they read emissions, the further away it is the less pressure / emissions it will read. The first and second communicate with each other. The 2nd makes sure that less emissions are passing it than what the first read. So I'm assuming that leaving the first one on will make it so the 2nd one reads more than it should. You should try and get it off if you can.

 

Use a o2 simulator.... on the post cat sensor ...

 

That makes sense, but why did the CEL turn off? Is this just temporary? And is there a way for me to get this spacer unstuck and get off without causing any damage?

What's an o2 simulator?

 

The computer reads the first O2 and compares it to the second O2 reading and determines if the CAT is working good. An o2 simulator is a small box about the size of a match box and it connects to your 2nd O2 plug , it keeps telling the ECU a constant signal and therefore your ECU thinks the CAT is working falwlessly when in fact you may dont have one at all.. You can remove it along with the 2nd O2 sensor using this..O2 SIM

 

Few things...

First off, the cel may have turned off because you reset it... . Mitsubishis read their computer status every 40 or so miles (it's more specific than that like 35.8 or w/e but i can't remember the exact number). So if you drive it for 40 or so miles and it DOESN'T come back on, you're in the clear.

Second off, the person suggested using a o2 simulator / eliminator at the 2nd o2 sensor. You may have to use 2 to get it away from the exhaust enough. The problem with that is you may not have enough room.

My suggestion is to use SOME sort of anti rust spray on the eliminator you used. Keep spraying that *** until it comes loose. Remember that tapping a wrench is more effective than forcing it. Forcing it will break / tear quicker than tapping it. Use a breaking bar and tap that bastard until it comes loose. Good luck dude

 

i don't see how it could have become stuck in place after one day. did the person who installed it cross-threaded the crap out of it while slathering it up with epoxy? you should be able to get a wrench on that thing and give it a twist. try using a breaker bar on the end of the wrench.

if all else fails you can go the electrical route: http://www.adaptiveperformance.com/MILELIMINATOR.htm this is the closest product i could find that was like the one i purchased from a webpage that isn't around anymore. splice it directly into the 2nd O2 sensor wiring underneath the carpet on the passenger side of the car and you're good to go.

 

Try to take out the RRM eliminator while your engine is warm. Exhaust parts can seize up, even when installed properly, after some heat cycling and taking it out hot can make it easier. Just make sure it has cooled off before you put the sensor back in.

 

I guarantee you can get that out with a warm engine and a breaker bar. Make sure you use a breaker bar though because you don't want to tear anything and you'll least likely do it if you're tapping it vs reefing on it. Please update us, we're all in suspense