Weird. I pulled the cat and muffler off Casper (05 Silverado) and so far for 3 days, no EGR codes!

Odd. Big Blue (04.5 GMC) threw codes with no backpressure.

Have all the LLYs thrown codes with these mods?
Or is it a few will and a few wont?

I threw a code once after removing the cat. That was after a few days. Cleared it and it never threw a code again until I unplugged the EGR.

So does that mean your going to pipe it right off the turbo and through the hood with a flapper?:ro)

Have all the LLYs thrown codes with these mods?
Or is it a few will and a few wont?

It depends what emissions you have by reigon.

So if you live in an area that dosent require emmisions testing you can pull the cat and straight pipe it with no codes, but if you live in an area that has testing the truck will?

Now im lost:eek: Then that would mean that the programing is diferent on each truck depending on where its sold? That dosent make sense to me:o: Did i understand you right?

It depends what emissions you have by reigon.

The newest LLY programming has loosened up the P401/P404 parameters...

The newest LLY programming has loosened up the P401/P404 parameters...

That's what I'm thinking.

It has to be the name "Casper" that scared the code right away from it!!!

Congrats on no code!

But isnt going with a catback 4inch system and keeping stock exhaust and losing the cat going to do about the same besides maybe hearing the turbo better "cat"less?

I am at a loss as to which one will be a better "performance" mod.

I want the turbo to whistle VERY loud but not at the cost of throwing codes and geting warranty hassle at the "Stealership"!

Now if anyone knows a way to run a catback but make the Turbo Whine like a baby than problem solved!

My truck hasn't thrown a code since I straightpiped it... Maybe the 3.5 inch stock exhaust has enough backpressure for the egr...

My truck hasn't thrown a code since I straightpiped it... Maybe the 3.5 inch stock exhaust has enough backpressure for the egr...

Is your straight pipe 3.5 inch? I have been wrestling with going to a 4" straight pipe (or a kittyless MBRP) in place of my stock exhaust, but don't want to throw codes or go the fingerstick / egr blockerplate route.

Thanks,

Bud

My truck hasn't thrown a code since I straightpiped it... Maybe the 3.5 inch stock exhaust has enough backpressure for the egr...

And that is all you've done? No fingers or egr plate?

Hows the sound? Can you hear the turbo whine alot more?

And last do you still have the cat in place? My main objective is to just have alot of turbo whine....I like the way it sounds when you take off and it sounds like an F-14!

Performance of the truck is more than plenty for me!! Although I have an Edge EZ coming with some gauges.....never know when a stroke or a cummins might wanna try to pick on you!:lol:

No finger stick or egr plate, and no codes any of the times I have checked. Just faster turbo spool and way better sound.
I just got an 03 lb7 exhaust from a buddy that installed mbrp and used his front pipe inplace of my front pipe. Then I took the part where it curves down around the crossmember after the flange and put that where my muffler was.. It was the perfect amount of curve to fit where the muffler has one end come in the bottom and the other out the top. So it is 3.5 inch stock pipe the entire way back. It sounds really good, quite a bit of turbo whine, and growls really nice under load. I love it. If I had a place to host some videos I would let you hear it.. I'll see what I can do about that..

I had no cat and a 4 inch cut out right where the down pipe ends on my truck, never threw a code (used to drive it with the Cut out open). then when i got my five inch, and the codes came. so a catless stock sized down pipe flows less then a Full Five inch exhaust with a muffler?

Well in all research I've come up with on my 05. I have came to a conclusion.....If you want a good running truck with no codes and no problems....leave it alone!

If you wanna "risk" it than leave the cat where it sits and forget about it and just put a piece of straight 3.5 in pipe where the muffler used to be.

Or, go with straight pipe off the turbo and 4or5" all the way back and start having codes and then buy the fingers and egr block and still have codes every now and then.

Am I right? this is just my conclusion.

I think I am going cat-back exhaust and a edge ez with a intake and sit back and enjoy no tranny problems and no codes! "Hopefully"

All this is definately complicated to decide what is and isnt worth it.

The 2004.5 LLYs were very sensitive to backpressure changes from exhaust mods. The '05s seem to be less so.

Knowing exactly what you can get away with is hard to predict. My advice, for what it's worth, is get the exhaust you want installed, then see if you need to cure the codes. If so, you know where to get the cure.

Blocking the EGR is a whole nuther topic...............