i currently have a 97 with a 5.4. its got stock exhaust manifolds to stock y pipe to a si/do flowmaster 40 duels out the back, thinking about getting rid of the stock cats and replacing them with some high flow cats. im hoping it will make it louder. How do you think this sounds and do you know of anyone who has this?

 

Hi flow cats are pretty much a waste of money. They might flow better, but they're not as loud as advertised. You should have 4 cats on your truck. I recommend cutting off the back 2. They won't mess with your engine, the first cats do your air/fuel ratio. But I heard there was a small chance that your CEL could come on. But if u don't want to do that, Cut out the muffler. I have true duals no mufflers and I think that sounds best by far. I've had the 40 series, and the super 10.

 

^ x2.. "high flow" cats are worthless lol

 

well im not gonna replace with straight pipe and take a risk of throwing a code

 

Just cut em off, get a pair of glasspacks

make sure you'll pass emissions though cause I'm pretty sure it wouldn't where I live

 

or just don't cut them off at all and run glass packs or straight pipes from your cats back haha

 

I usually remove the cats off all of my vehicles but i recently installed a set of high flow cats on my supercrew into a 2 into 1 magnaflow with a 3" replacement magnaflow tailpipe and the truck is still a little loud for my taste.As for glasspacks,I'm pretty sure nothing sounds WORSE....

 

nah, they sound fine. lol

 

I cut my back 2 off, replaced with pipe, and no muffler and its got some attitude to it. My cell was on, but my programmer said it was the front two o2s were bad. It had nothing to do with the back 2.

 

LOL! It's all personal preference!My 94 has a 351 with 1 3/4 longtubes and 3" dual exhaust with magnaflows and sounds great up to about 3000 rpm then it gets obnoxiously loud,need to add another set of mufflers i guess!I'm sticking with the stock catback on my gt as it does'nt seem to be hurting it's performance any...I just can't handle the noise i guess!