I just replaced my left front wheel bearing and one of the Map sensors then went for a test drive. I was on it hard hitting 20# of boost then boom! Looked in the mirror and saw a grayish smoke. I pulled over to look under the hood and saw nothing out of the ordinary and it was running fine. Get back in and start the car and now it’s pretty loud! I have a full Miltek exhaust so wondering if it blew a baffle or something. I also got the after 02 sensor code which don’t make any sense since in my custom tune the rear is turned off?

 

Found the issue the guts in the cat must have been plugged and blew out. I dropped the exhaust and the cat was empty and also took out the rear 02 sensor. So that must have been causing my map sensor issue. Just need to figure out why it plugged up?

 

No pre-cat, maybe? The pre-cat is designed to deal with a rich mixture after a cold start. If it's not there, presumably the main cat has to try to deal with it, can't & gets plugged up.
Just my guess!

 

Good guess but these only come with one cat