Here's my story. I have a 408 making over 500 rwhp. Slp long tubes,3 inch true duels, high flow cats with bullit mufflers that dump at the axle. Car has 13.5 compression with a cam that specs out 257/263- 64x/64x. Car is extremely loud. I like loud but this car can be heard for over 1/2 mile away. I gutted the cats and am putting a cutout on each long tube. I am then going duel 3' into a flowmaster wye. 3 in. out of the wye then over the axle into a flowmaster stock size muffler single in duel 2.5 out into dual/dual tips. I have not had a stock style exhaust on my car for a long time. How much different will this sound then my current setup. Will I have any rasp on a wye pipe setup that I didn't on my true duels. Neighbors are not happy with my 3 AM returns from racing on Friday and Saturdays. Need car to be somewhat quiet but not sound like crap.

 

With what your going for it looks like it will still have a nice tone, but not be obnoxiously loud as what you have now. If it is to loud for you after you put all that on, just toss in a dynomax bullet in the i-pipe and that will help quiet it down a bit more. Get us a vid of what it sounds like now, i can't stand having my car quiet.
-Joel

 

You will def have some rasp with the Y pipe setup....