I'll be installing my PS Lt's soon and have been planning out my new exhaust. In WI we gotta run cats because of emissions checks, so I'll be getting my factory cats welded into the setup, but I'd like to do 3" off the collectors, duals back to an x-pipe and then 2 magnaflows and I'm still not sure if I want to dump it or run side exit infront of the pass. rear tire again. I've read around that 3" can be overkill and you lose a lot of lowend torque and even hp? Tell me what you guys think!

 

I would stick with the 2.5 true duals or a 3 inch cat back. True 3 inch might be a lil to big for a NA 5.3, actually hurt low end

 

3in all the way i picked up .15 going from 2.5 ture dals to 3in ture duals if i can find the chart i had it would tell you from this hp to this hp you need this pipe and so on. i will look for it. but i would not runanything smaller than 3in

 

Yes please post that info up.. Thanks

 

3" is faster at the track, but I can guarantee you 2.5" makes for better part throttle response and power than 3".

 

if i recall i seen that chart also, i used to run true duals with a fully bolted head and cam 5.3 IT SUCKED, LOST TREMENDOUS back pressure and low end tq. if not mistaken the chart for 3" true duals is if you have plus 400 rwhp

 

the cats will control backpressure more than your pipe size. if you were running no cats i would say 2.5. with the cats in place i bet you will see no difference either way.

 

Here are a few charts

 

For that 5.3, you don't need anything over 2.25" duals. In fact, 2" duals would be enough.