Does anyone here know the thread size of the o2 sensor after the cat? I know that the actual sensor is 3/4 inch but what is the size of the bung that the threads go into? Reason i ask is because i bought a spark plug antifouler/spacer to try and get rid of my CEL from my downpipe and i THINK it's 18mm but before I go install the spacer just making sure 18mm is the correct size. This is on my 07 SS/SC.