My car is confusing the heck out of me. I am the second owner on the car and I can't tell if the guy who owned it before me did a l61 to a lsj complete exhaust swap. The pipes just seem to be big to me. Does anybody have specs on the OD for the downpipe, header, and catback for either of those cars? The two 02 sensors are both on the down pipe. My car is making me feel like a complete retard right now so any help is appreciated!

 

The only way I know if to tell the difference between headers is to look at the outlet, if its a circle it's an lsj, if its a D it's a l61. For the down pipe, the inlet to the cat is 3 inch outlet might be the same with a step down to 2 1/2. And lsj catback is mostly 2 1/2 inch it has a pinch point somewhere around the rear axle. I forget exactly.