Well I have a 02 avalanche with the 5.3 and wanted to free the exaust up a little but didnt want to hear it (I have had alot of stuff and am just tired of the loud stuff). Well I got a y-pipe from an 04 Tahoe and cut a somewhat flap in the cats and bent the metal back, then beat and scrapped all the inereds out. I then pressure washed inside them to get all the stuff out and bent the metal back over and welded them back up. Used stainless wire of course! So then I took about 45 minutes and pulled my stock y-pipe off and put it up for when I want to put it back on and put the new one on. Well I was kind of scared to see how loud it was going to be when I fired it up, cause I didnt want that but would live with it. Fired it up and damn I couldnt even tell a difference. If you listen very closely you can hear a little difference in the tone when your standing next to the pipe. Other than that it sounds the same at idle. So I took it for a ride to see if it helped any. HOLY CRAP, it gained a but load all over the power band. Down low got very touchy and up top it just keeps pullin unlike it didnt before. And I just dont see the cats being clogged up with only 75,000 and all stock. When taking off and getting on it its like I might be able to hear something but not sure. I know its the exhaust that im hearing but you cant tell its that quiet. This has to be the best thing that I have ever done to a vehicle to get the exact results I was looking for. So basically if you look at the truck it looks like its completly stock underneath. Remember I have the stock muffler under there still. Its just great that nothing was cut on my truck to do this. I will get a tune from my buddy here locally very soon, but so far the check engine light has not come on. I do have a set of O2 sims, but they are for a f-body. Ill let ya know when the light does come on though.

 

right on

 

I wonder if this would help my turbo spool up quicker???hmmm

 

awesome

 

Ok just went to lunch and damn this is cool. Its like free horsepower!!!! It pulls alot harder than before and still is quiet. Well I went probly 10 miles at lunch and the light hasnt come on yet. Has anyone ever done this and the light not come on at all? Im still gona get the tune, but if it doesnt come on I can waight a little longer to do it.

 

I am glad you like it. I also felt a nice difference up on top. I wonder how much rw hp they are worth in the dyno?

 

well i might check it out. Heck it wouldnt be that bad to run then pull the y-pipe off and put the stock one back in then run again. It would be a while for me, but maybe somwone has done this already and can post up some numbers.

 

The Fbody simms are probably working. I put my simms from a 96 on a buddies 02 work truck and they worked on his truck.
I think I'm gona gut or remove mine today

 

Well I dont have them on there yet. I was just gona run it and see if the light did come on, I have to dig around to find them. I just read your thread and would definitly recomend it. I did mine like I did for ease of placement and removal. It would flow a lot better if you were to cut them off and weld a peice of pipe there. Heck you can put the pipe inside the gutted cat and weld it back on if you want the stock look as well. Good luck on that 14 pass!

 

im going to be taking my cats off tomorrow and i cant wait for the sound of a catless.