If i replace my exhaust with new 4'' and remove the cat converter will it affect performance, and are there any problems i should be aware of? I have the AFE stage 2 with Hypertech programmer. Thanks

in my experience this seems to be 50/50... while some remove the cat and have no problems, I removed mine and had performance issues so I put the stock pipes back on.

I dont want to lose any performance since i pull a 29' fifth wheel. Maybe its not worth taking the chance. Thanks

Mine had no performance issues but it did set 2 egr codes P0404 and P0401 so I put it back on.

robo- You can go with a 4" cat-back system without any worries. The problems arise when you remove the converter. The EGR will throw 2 silent codes (if you have a federal truck) P401 and P404. If you have a Cali truck, your dash light will come on. I personally prefer removing the converter as the turbo seems to spool a bit faster and the egt's run a little cooler.

robo- You can go with a 4" cat-back system without any worries. The problems arise when you remove the converter. The EGR will throw 2 silent codes (if you have a federal truck) P401 and P404. If you have a Cali truck, your dash light will come on. I personally prefer removing the converter as the turbo seems to spool a bit faster and the egt's run a little cooler.
Do all LLYs set these two codes with no CAT?? The reason I ask it alot of members here say they have no codes with no CAT??? If so I may go back to CAT less.. it did help on EGTs

LLY's will set the codes. The CA and some NE trucks will light the light. Just because the lighit is not on does not mean you don't have a code set. You have to get a reader to dump codes to be sure.

Jim

I have the cats off both my LLY's with the stock exhaust. Neither have thrown any codes in the last 50,000 miles combined. I must be lucky.

Im just guessing here. but it should not affect the warranty? It sounds to me like this is a toss up. It would be nice for the turbo to spool alittle faster and run cooler egt's while pulling. I will just have to figure out what i want personally. Just not sure if the exhaust is worth the money.

I did have a 4" exhaust with no converter and it did throw codes then, but I also was running an air intake kit. Not sure which was doing it if not both. You should be able to find a stock 01-03 front pipe and remove your cat cheaply. Then if it doesn't satisfy you you're not out much. I found mine at the local exhaust shop. They gave it to me.

keep in mind...if you go to the dealer for anything and you have no cat, they will NOT even look at it. Unless you have a hook up. GM is clamping down on LLY cat removal.

the codes will not turn on your SES light, but if you put a scanner on it you WILL have EGR codes in there.

I just walked out and ran my codes with my Actron scanner. Nothing there. Hooked up my Predator. Nothing there. Hooked up my Quad. Nothing there. Aprox. 25,000 miles on this truck with no cat. NO CODES!

rick- If you still have the stock exhaust system, I am thinking that the stock muffler is giving enough backpressure for the EGR to work properly therefore not setting the codes. Just a thought.

That appears to be the case. When I had the 4" exhaust without the cat on I would get codes. Now I get nothing but a little less exhaust temp.

good to know..

Will a LB7 front pipe bolt in on a LLY? or are you guys getting a shop to make these?

Yes, an LB7 front pipe will fit. If you have trouble finding one, you can order an MBRP one for pretty cheap.

When you remove the cat and keep the stock muffer will it make the truck any loader? How much dose the front pipe run in price? thanks

If you add an EGR blocker plate and Finger stick, won't that solve the problems of throwing codes after you remove the cat?

I ordered my finger stick for the EGR blocker plate I also ordered but I'm thinking that even if I didn't have the EGR blocker plate, the Fingers stick would solve the problem of codes showing up after removing the kitty.

No?

Who would you recommend for a cat back exhaust? It seems the cat back systems are a little more $ than you can buy a complete system for, or im looking in the wrong places.

I think MBRP sells the cat back and talk to Mark Craig off of here.. he works at DPPI and can get you what you need. Mark Craig is also his screen name here.

If you add an EGR blocker plate and Finger stick, won't that solve the problems of throwing codes after you remove the cat?

I ordered my finger stick for the EGR blocker plate I also ordered but I'm thinking that even if I didn't have the EGR blocker plate, the Fingers stick would solve the problem of codes showing up after removing the kitty.

No?What is the finger stick?

its like an MIL eliminator.. or basically just fools the computer and does not set any codes for EGR.

the guy that made them goes by Fingers on here...thus, Finger Sticks