hi cb- this pre cat pipe is interesting.this was back when cats came out and were mandated by the smog laws. i think this was about 74. my 73 plymouth did not have one. in any event for a few years (only a few) after market car parts manufacturers started selling what was called test pipes which you could swap in and switch out the cat ostensibly to temporarily test the performance of the cat. too many folks left them in to get better mpg and performance, besides they were cheaper than cats and a boon to cheap bastids. soon the law got wise and stopped this. wondering if this item has made a comeback as a pre cat pipe for older cars(25 + years) in states that no longer emission check these old tanks. old fuds who are po and drive 92 and older volvos will no longer get soaked by dealers who want 1 g for a cat job. will the pc coppers be after such malefactors? thanks tons oldduke