I may be purchasing aftermarket headers for one of my projects. Most of the options I care to look at do not have O2 sensor bungs welded in them, so I'd have to purchase some and weld them in so the computer can work correctly. The bungs I see advertised for O2 sensors are M18x1.5 ... Is this the common size for O2 sensors? Are there other sizes? If so, what do those apply to?