How did the truck accomplish this with an exhaust mod?

 

Do not know. Not my area of expertise, it just did.

I'm a tad "focused" on such things- measure my mpg at every fill also. Someone else would have to explain that. Was it going from 2.5" out to 3" out? Losing the stock "oil drum" of a muffler for the Super 10? Again, don't know.

 

If I live in Cali then no, you gotta leave it stock.
What year truck are you? I know on the 97-03 you can remove the front 2 with no problems, but i think its the other way around for 04-05.

 

You can change them over to a 2-cat system if you like. I'm not really sure why they started off with a 4-cat system. If you were going to go that route, I'd probably just get LT headers and hi-flow cats. It's not a cheap mod, but you'd probably gain a good bit of HP/TQ from it.

 

I also don't believe it did anything for the RPM drop. The torque converter running steady at 75mph should be locked up, which means RPM will be dependent on wheel speed/gearing.

 

No reason to cat-less on an on-road vehicle. The hi-flow cats out there have minimal effect on performance, especially with the power levels this engine is capable of making in most trims.

 

Well, I won't try to convince. It just is.

I notice right off that the engine seemed to have more mid-range and slightly less low end- it isn't working as hard at highway speed.

Like anyone else, I know my truck. Nothing else was done to it at the time, still running same canned tune.

Anyway...also looking to have cats replaced...noticed some rattle underneath in vicinity of one, wonder if it might be done. Thanks for the mention Dunesgirl- gonna look into a rework under there.

 

The reason for the low end loss is the slowmasters. The chambers restrict gas flow at low rpms.

 

I have the 14" Magnaflow on mine. While it is nice at idle and when you step on it, I will not take it for a long drive on the highway. Anything more than 1500 rpms for a long time and it will drive you nuts.

 

Guessing not a fan?

It's just what I went with at the time, cost was a factor, and I ain't flashy or nothing. Not married to any brands really- just don't know enough about 'em yet. At first I was sorta bothered, but as the computer adjusted itself over the next couple weeks, I barely notice now. Plus...I figure I ain't looking to race off the line, but I do have to ride the highway to work, hunt, camp, etc. so the trade-off isn't all that bad. I can live with it, but who knows what the future brings. I still don't use the radio much...the exhaust note is my radio for now.

I'll keep studying though!

 

Ha not really a fan on flowmasters,. I don't like the sound (obviously an opinion everyone likes something different) and don't like chambers that are restrictive. The trade off tho if you like the sound is minimal

 

I always thought the 4 cat system was left over from the 5.4 always having 4 cats. Maybe not directly using the same exact parts, but maybe the concept of having 4 cats was just a transition because that's what the old engine had.

Utah (or Colorado?) has pretty strict emission standards, don't they? If they're picky and thorough, they may or may not, but in Texas, they don't actually climb under the truck and look unless there's a reason to. Each state, and more importantly each individual inspector, is completely different. Some don't care, do the basics, give ya sticker. Others climb all over the thing and make you fix every last imperfection. Most of the time, Magnaflow hi-flows will pass inspection and won't trigger a check engine light, but it has been known to happen. Just a risk you'd have to take, perhaps after talking to someone that knows exactly how Utah's tests are.

 

That's why I love Michigan no annual inspection

 

^Try telling your Indiana neighbors to adopt that policy . . .

Edit: actually, it looks like they don't have an inspection except for in 3 counties. So that may be awesome for my little sitchiation haha.

 

I'm not totally sure about Colorado's emissions standards, but currently in Utah we have a few counties that require emissions testing. I just happen to live in one of them. And you're right, I even know which shops would be more lenient. I guess when I get the extra cash (once I'm done with all the maintenance stuff first), I can take it to an exhaust shop and see what they say. I'm generally looking for a SIDO setup.