Ok, I want to get my exhaust done this week on my 01 Screw 5.4L and I wanted to ask you guys what you think is the largest and smallest size pipes I could use? From what I have seen most of the pre-made setups are using 2 1/4 with a Flowmaster super 40 or a regular 40 series muffler. I plan on keeping the Flowmaster muffler but wanted to know what you guys thought about going with 2.5 inch piping.

 

You should be ok running a 2.5in pipe. I know I few guys running 3in all the way back

 

I have 2.5running all the way back and love it. You should be fine doing that. You get a little deeper sound that way.

 

I'm running 2.5 inch with a Flowmaster D series 50...sounds gr8 ..the 40 will be louder...hope thats what you want.

 

Sounds good. I will take a look at the 50 series. I appreciate the help gents.

 

I remember reading that a dual 2-1/2" system with same sized cross-pipe after the cats will handle up to 400 horsepower...an improvement over 2-1/4" pipes even on stock engines. Larger than 2-1/2" with less than 400 horsepower will just hurt performance. Will cause a loss in HP and Tq.
In any case, a cross pipe of same diameter on true dual systems will help bottom end torque. An "X" pipe after cats improves scavenging and can improve performance over a straight cross-pipe, but the "X" will give more of a raspy NASCAR sound and the straight will generally give a deeper tone, which I personally prefer. Good luck.

 

Another question for you exhaust guru's. What size muffler do I need? I went to buy my muffler today but I wasn't sure of the size that I needed. Any help will be appreciated.