02 Sensor problems...Need minor help

[RichieRichJP]

Well to keep everything short because there is no short way of explaining the problem itself, is there a EXACT distance that the REAR 02 sensor has to be from the cat?? My rear 02 sensor isn't plugged or screwed in anywhere so the guy at the muffler shop has to make a hole in my pipe to get the 02 sensor in and weld it on. So basically, I've been running around shops all day trying to get a universal 02 sensor, which no one has, and trying to find out where I can get that 02 sensor welded in. Please any ideas...Once I get this god damn thing working I'll have a fully working rippmods/exhaust system, its just that stupid 02 thing is holding me back. Talk about laaaaag