hi guys,

i'm pretty new to the car modding scene.
today i was taking of my stock downpipe to weld a bung for wideband o2 and stripped bolts connecting downpipe to o2 housing.

how do i remove the piece of bolt that is left inside o2 housing?

and in general are there some higher grade or something bolts that i should use on exhaust parts?
the ones that were on my car there badly rusted. i don't think they were stock. they didn't have springs on them and were size 14mm, while stock i think is 17mm.

i want to replace them with proper ones so they don't brake every time i need to install some exhaust parts.

Thanks!

 

and one more question: what is thread size of the stock bolts connecting downpipe to o2 housing?

Thanks!