I realize this subject has been beaten to death, but this is more of an opinion/personal experience based question. I'm in the middle of installing an agency power single, stillen y pipe, and no name test pipes. The cats are still on the car until I take them off tonight, but I've been tossing around ideas in my head. I was considering leaving them on, just because there would be no hassle come inspection. The only thing is I don't want to be underwhelmed. I was hoping from these mods I'd have a decently loud setup. How much are the cats really going to hold back? Is the difference extremely noticeable? I've read it is but I'm just looking for reassurance I guess.

tldr; AP single, Stillen Y-pipe...test pipes or no test pipes? What's the difference in sound between cats and test pipes with those mods?

 

It's already going to be significantly louder because you're running a single. You'll more than likely see a big difference in sound if you go with the test pipes.

 

You're going to be deaf either way.

 

It won't be nearly as loud if you keep the cats on. Biggest reasoning behind swapping to test pipes should be the performance gain. If you "don't like the smell, or it's raspy, or it's too loud, or it drones and hurts my little baby ears" then keep your exhaust stock.

The performance gain should be worth the couple hours it would take to swap in the cats for inspection once a year.

 

Test pipes are probably the best bang for the buck mod.. Here is my setup:

-Stillen intakes
-berk test pipes
-stillen y pipe
-agency power single