My brother has a 03' 6.0 and wants to upgrade the exhaust but keep price down to a minimum. I did a search on that and seen people that have cut out the factory and replaced with a Flowmaster. Would that improve performance with a muffler or go straight pipe. He put a K&N filter charger system on and needs more flow cause it actually make pulling power worse.

When I had my 96 chevy 4x4 I put a flowmaster on it and didnt like the sound it sounded too much like a 5.0 mustang, I took it off and put the stock muffler back on 3 weeks later. Your not going to notice any HP increase buy just putting on a differant muffler it will sound like there is more power but not really.

I know a guy with a half ton 5.3 that just has it straight piped. It sounds pretty good, suprisingly not all that loud. Do keep in mind that it is illegal to do so, and coppers love to give out loud exhaust tickets.

I have read that alot of people are getting good results when they run a Magnaflow system on the 6.0's.

William

I ran dual strait pipes on my 7.4{454} when I had it.I never got pulled over. It was very loud but just what I wanted.Too bad my D-Max isn't even close to that loud strait piped.

Your not going to notice any HP increase buy just putting on a differant muffler it will sound like there is more power but not really.
how do you figure that one?? increased air coming into the engine and increase exhaust leaving the engine, why would you not have an increase in power??

i put a flowmaster and k&n on my old truck (89 350 k1500) and definitely noticed more responsive acceleration and a slight increase in mpg. that being said, the exhaust on these trucks seem pretty free-flowing on their own. if you have ever seen the inside of a flowmaster though, there aint much restriction. anybody ever cut one of our mufflers open when they pulled it off?? just wondering what its like inside. i think i am gonna add an air intake first and see what happens.

Had a 93 2500 with a 350 I took the muffler off and ran straight from the cat back. Sounded good too. Only time I worried was coming back from Granby headedup the hill we passed the yocals with the windows down. Light footed it by and got back on it after a ways. Never got stopped anywhere for it but I was sure nervous that day. Had a 16' enclosed on and loaded down so it was hitting hard to.

i was in the same boat. Wanted more sound and possibly a little more power and fuel economy, but didnt want to spend alot of dough. So i bought a stock catback from a Ford Diesel (3.5" stainless) that had been removed at a exhaust shop and had it installed/mated to my stock cat just using the over the axle portion without the muff. SO 3.5" catback straight pipe for about $75 installed i feel is a pretty good bang for the buck. It sounds great, but actually i wish it was a little louder!? May have to get some newer higher flowing cats to increase the sound a bit.


NOTE: i'm referring to a F250 w/460 and you guys are blessed with much better flowing cats, thus louder.

Im running dual 40 series flowmaster on my 2002 6.0 2500hd and its loud, louder than my cousins 5.7 with straight pipes. But then again im runnin 2 true duals. Correct me if im wrong but isnt it legal to run straight pipes on a 3/4 ton i was told they dont have to pass emissions but i may be wrong.

They still have to pass emmisions but do not have to get run on the dyno. My 98 K2500 vortec 7400 passed two emmission tests over the years I owned her.

straight pipe shouldnt matter with emissions as long as you still have the cats, right?

Emissions may not matter but there are noise laws that must be complied with, your'e probably right about it not mattering. I don't know if mufflers have any catylizing effects or if their strictly for reducing sounds. They certainly won't fail you because of noise at the testing facility.

I don't know if mufflers have any catylizing effects or if their strictly for reducing sounds. They certainly won't fail you because of noise at the testing facility.

to the best of my knowledge, mufflers have no catylizing effect. They only 'muffle'

Yeah, i would definitely worry in some places about having too loud of an exhaust. Would probably fall under the same rules as having too loud of a radio. Anyway, straight pipes with a cat won't be too terribly loud. You will probably get a "popping" sound more than just a deep thrum though. For loud, go straight, for a clean or deep sound, a muffler is the way to go.

Soon after I bought my '98 5.7 GMC I had a custom bent true dual system installed right from the dual cats back, no muflers. It was way too loud! And I was young and dumb then! I thought it would sound good cause I had a '87 5.0 stang with true duals, factory cats and no muffs, and it sounded good! I had mufflers welded in within 2 weeks on that 5.7!