I just bought a new omni test pipe. It is adjustable, and I was wondering if I had to weld it after I fit it to my car. It has a removable center section that you can adjust to lengthen or shorthen the pipe.

 

I would weld

 

i welded mine. its built so you dont have to though. the carbon build up is supposed to seal the pipe or something

 

2 of my friends have them. Neither of them welded theirs and they seemed not to leak, but my one buddy's motor apparently moved quite a bit while beating on it, and it slipped out of place. I would recommend at least tack welding it.

 

just go to a muffler shop and have them take the cat off and weld a pipe on...its cheaper and better...or take your cat off and gut it