I know a 4" from headers back would be best but I want 2 pipes coming out the back. What if I did a 4" from LTs through muffler then a y pipe with two 2.5" pipes coming out the back. would it defeat the purpose. Not sure if I want to do it this way or just do 3" duals.
_____

 

Would work just fine and not affect performance at all. Do it!!

 

Dual 2.5 is smaller than 4, you need dual 3 to not neck down.

 

ok then no 2.5

 

Run run 3" dual front to back and be done with it.

 

I have 4" headers back to a Y. My Y is simply for 2 tips which are side by side out back similar to the stock location. What are your plans for muffler etc and how loud do you want it? I have catted LTs with a 4" in/out 20" case magnaflow and mine is louder than most guys would want and it droans like a beast! So my recommendation is if you go 4" do your research if you want to avoid drone, find a resonator or something and/or a longer muffler. Otherwise run dual 3" as stated, you have far more muffler choices with that route.

 

no drone and I want to be able to talk to the person next to me with out raising my voice.

 

necking down a little bit is fine & helps keep exhaust velocity up at the back end. have you looked at large HVAC systems? they start with large ducting close to the pump and step down smaller as it gets farther away so that the air comes out the vents at the same rate. i remember an old hotrodding article from a few years ago explaining in more technical terms how that applies to vehicles, too.

personally, i'm using a slight step-down on both my vehicles and they run & sound great. the truck has a stock 5.3 running 1.75" LTs, 2.5" Y into single 3" then through a dual-out muffler to 2.25" tails and 3.5x22" tips to deepen the sound. the car's TVS2300 LS1 @ 11psi has 1.875" LTs to 3" X and 2.5" axle-back

 

Sound clip plz!!