I found someone selling a custom-made high-flow straight pipe for my maxima, says will add 9 - 16 hp, should i get it?, 2.5" diameter...?? its cheap, plz respond

I don't think it will add that much horsepower. Btw, how much you're getting it for? Let me know because I'm interested in getting a straight pipe too. Isn't it call a test pipe?

i say yes. i am running s straight pipe and it sounds great.
i had the apexi ws exhaust and it was to quiet, way to quiet. so i had an exhaust shop remove the cat, and the resonator. trust me it sounds great. it is not to loud, and i can feel the diffrence from when it was restricted. all i have to do is get my y-pipe and it will sound even better. it sounds like an m3 right know thats how deep the tone is, so go for it. don't forget i have a world sport muffler, it was designed to be quiet, so your muffler might be a bit louder, go for it anyways. post the results

as far as i know the straight replaces the cat, and if you get a y-pipe that replaces the straight you have. isnt it also very illegal to replace the cat with a straight?

Yes. Don't do it.

My dyno butt-o-meter says its worth a few hp. It is illegal, when you have to go and do your inspection you should put the cat back on. It would be best to save this one for later and save up for some other mods like an intake or exhaust or y-pipe.

Very doubtful that it will add that much power. He's tryin' to sell ya'.... If you have to change the cat out everytime you need an inspection, that's a pain in the...
Not worth it....

Yeah, we don't really have to worry about that, right Matt? :) In Louisiana, we don't really have a law against this. As far as inspection, in my experience, they never check a thing like this. However, I might get a Apexi WS exhaust first. Then, maybe this test pipe.

I felt that it was a improvment over the RT cat, so before you do an RT get the straight pipe.

As fas as a pain to swap, I do it in my drive way with hand tool and a floor jack in under 20 minutes. Its four bolts thats it...