Right now I just have a flowmaster muffler on my 97 f150,I think its a super 44 it was on their when I bought the truck, but it's a si/si side exit and I've been wanting t change it up a little. I have the 5.4, but my first plans were to run true duals with an h pipe and 2 dyno max bullets because I think it would give it a nice deep sound that is pretty loud, I want it to be loud but not quite like straights where it cracks and popples alot. My new idea was to run just starights with a y pipe to split it, and then run an electronic cutout right before the y pipe so that i could adjust the back pressure and the sound. But my question is whch will do better for performance and mpg? I have a k n' n air filter with the stock air intake mod but nothing else done to the engine.
Thanks

 

I don't blame you for wanting to change it if it is a si/si. That would cause excessive back pressure!

 

SI/SO actually performs the best, opposed to 2.25" X piped mandrel true duals. Nothing like the power of a full mandrel 3" single.

For economy, opening up your size will help some, 2.5" duals will give you great highway mpg.

 

Ok well what about the idea of running straights but adding an electric cut out, but I want the cutout to be in the pipe so that I can adjust the back pressure as I want it. Does that make sense? Also, I don't mind the performance of my truck now because I really don't need it to be any more powerful other than personal enjoyment, but I drive alot so improving mpg would be a big factor but I don't want to lose any power. I would'nt mind gaining some low end, but as far as mpg I do alot of highway driving. And I want it to be loud. I love the sound of true dual straights with an x pipe, but I just think it would be cool to be able to adjust it with the electric cutout.
Thanks

 

Is 15-17 great??

 

Electric cut outs have sounded horrible on any street vehicle I have ever heard.

 

Thats my highway economy now. Went down from 20.4mpg highway to 15 - 16 at 70mph.. damn Toyos.

 

12 mpgs right here.
OP--- change all your piping to 3" from the Y back and then add a single dynomax bullet.