There is another member with a setup like this but instead of hijacking his thread, I'll start a new one. My question is:

How restrictive is the stock muffler?
What is the measurement of the inlet stock muffler?

I plan on doing my own custom exhaust with x pipes starting from secondary pipes to stock mufflers. I want to go 2.5 inch x pipes to straight pipe on stock mufflers. Anyone with ideas or tried this already? Its going to be on an 07 is350.

Note: I already looked into full exhaust systems and I really want 2.5 inch pipes and to retain my stock mufflers. Otherwords, not interested in other mufflers or exhuast setups.

 

Grab some calipers and measure the piping leading into the rear of the mufflers; my thinking is it is slightly smaller than 2.5".

GL with the setup, and post pics and a vid of the sound!

 

I actually decided to go ahead with x pipes. The stock muffler inlet is 2 inch. I went ahead and removed my secondary cats and did a full true dual 2.5 exhaust to the stock mufflers. Its a really quiet set up. I'll try to take some pics. As far as gains go? Low end torque is definetly improved. Mid range feels the same but high end is definitely there.

 

Do you have any pics of your setup yet? sound clips?

 

I am busy this week but will post and share results later this month