Hello some rookie exhaust questions . I have an exhaust leak and it lit the check engine light but then it disappeared and has not re appeared . I did not get the code # from the kid at auto zone, he just said it was an exhaust leak. , my mistake for not getting the # . I put my hand by where the header flange and cat pipe flange connect no air blowing there . Once it quits raining I can put it on ramps and maybe use this epoxy Muffler weld to fill the leak? My big issue is I want to know if the leak can cause a sensor to read wrong and freak out the computer fuel and air delivery at highway speeds 75mph. I was told a while ago that the leak is caused by dissimilar metal connections on the cat pipe and ate a couple spots away?, but I do not know exactly where ? Thanks for any advise . If I need a cat pipe . I should not need the header ?I would think the cat pipe (with cat included) and a flange gasket is all I will need?r is there other pieces I am leaving out ?

Go under and look at it, post pictures of what you find.
That muffler cement is just a bandaid, won't solve anything. If the leak is bad enough it can cause issues with the a/f sensor

If it’s just leaking at the flange then new gaskets is all you might need. Depends if anything is cracked and how well it comes apart. The cat is serrated from the header on an Ex so you only need to replace what is bad. Not sure if they typically come with new gaskets or not.

Needed cat pipe sensors and muffler resonator and pipe was deemed good Thanks to all

Hope the sensors were Denso/ntk

234-4123 OS0115 ,234-4992 OS01010 WAS ON THE BOX Maxfavor is the manufacturer had I will get the Densos and send these back thanks for the tip