How substantialy will the noise level increase from both the interior and exterior if I install a Stillen Y-pipe? Currently I have a Stillen Hi-Flow Intake.

I will appreciate any feedback on this from those who own it or used to own it...

Thanks!

 

Not much, will give the car a slightly raspier sound. Not very noticable but it makes the engine sound nice. I had this exact setup 2 years ago.

 

Here is what I observed when I had my WSP Y-pipe. It should be somewhat similar to the Stillen Y-pipe.

-The engine note itself changes. The engine has a harder edged sound and is somewhat rougher around the edges. The aftermarket Y-pipe has different pipe length between the pipe leading towards the front exhaust manifolds and the pipe leading towards the rear exhaust manifolds. This causes the exhaust gas pulses to collide which is probably the cause for a slightly harder edged feeling engine.

-The exhaust note changes also. With the factory B-pipe, you'll notice that the muffler gives off a very low rumble at idle. It sounds pretty neat when your car warms up after a cold start. The slight rasp exhaust note around 2,000-2,200rpms (when the variable capacity muffler opens up its internal valve) in the stock setup is slightly amplified now. If you get off the gas with O/D off at any rolling speed with every accessory shut off, you can hear the exhaust note "roll down" the tach with a low rumble.

-The intake note also changes. The low growl you hear without the Y-pipe now changes into a dual tone unit. You'll hear the low-growl, but now its matched with a "chain saw cutting through wood" like sound after VI switches over to its short runners.

Conclusion, IMHO its well worth the less refined nature for the 13-17fwhp increase. The things I mentioned above probably isn't sensed by an average JOE or consumer, I'm just an **** person when it comes to these things