Very nice Lance and thank you! Now am can squash my suspicion that the IS-F had any sort of bypass valve in the exhaust. I didn't realize the IS350 had this valve and while doing some Google research I also discovered that the Prius and Camry Hybrid utilize the bypass valve feature.

 

Those F mufflers have several chambers and several different size holes for tunning

Joe Z

 

Well now we all know. Thanks for the analysis guys

Lou

 

YEs Stock intake.

I should have been more clear....and I did update my original post
The sound is not gone per say....its just not as loud and aggressive...the note appears but its lower in volume and also lower in tonality...

so it just doesnt sound as "split personality" as stock does...

The start up sounds meaner and the regular driving sounds deeper also...more 8 cylinder sounding if you know what I mean.

but that louder "VROOM" you get is there but noticibly lower in volume than stock....still sounds good tho just not as loud...
I would've liked it as loud but lower toned like it is.

all in all Im ok with it all around ...cause driving it around it sounds meaner.

I did it for the audio anyways....exhaust gains (if any at all ) are minimal
or what i like to call "unfelt" (mental horse power IMO)

 

Good Info, thanks again Lance.