the story : a6, 01 2.8 Q , i did the a4 code when i had k&n air filter, and stock exhaust,and it give me better gas mileage and good acceleration.now.. i remove the resonator and the mufflers and replace with 2 , 4inch mini mufflers and 2.5 pipes and 2 oval mufflers magnaflow all of them, so 4 mufflers total and bigger pipes.
the Question....after changing the exhaust i fell the car is more laizy than beffore and drops the mpg a lot. why ,? do i need to chip the car to find the right balance air-fuel-exhaust?or just go back to stock pipes and forget the "performance"?

 

2.5 is a bit too big so you will lose some TQ especially down low
I wouldn't go larger than 2.25, but give it some time to adjust, do a few WOT runs and see if it changes.

are those mini-mufflers you're referring to actually resonators?

 

i went with this as a muffler :
MagnaFlow Muffler 5" x 8" Oval 18" Body 2.5" part# 12256
and this as resonator:
MagnaFlow Muffler 4" Round 14" Body 2.5" part# 10416
i should change the pipes with 2.25 or 2.. or stock, or put back on a6 .... i feel like i waist money , lose tq and mpg for only few db more of the exhaust

 

What's all this about a K&N air filter + a code improving gas mileage?

Are there any other low-impact after market parts I should consider getting, or codes I should consider changing.

I have a 2002 A6 3.0 quattro, 57k - automatic tiptronic transmission

 

You might not be getting enough pressure build up in ur exhaust... id say add more power if you truely want to use that 2.5

 

I would say lose the mufflers you put in the center and put strait pipes or a X pipe in place of them. That should sound better and free it up more but I dont Know why your losing mpgs. I probably gained 5% on fuel economy when I changed exhaust. Post pics and vids of that exhaust man!!!

 

http://www.youtube.com/watch?v=RgtGM32qKu4 windows open and from outside:
http://www.youtube.com/watch?v=J5GDjsg0TSc
not sure if i will keep them i loose power, tq and is lazy , or maybe i will try to chip or something...or stock and recode on a4 , that was the best so far ( good tq, and best mpg +50 miles /tank)

 

Your exhaust sounds like a turbo back exhaust with out the exhaust... it really does sound great and performance like. I believe you are just missing the power. Nice sounding though.. get some clips moving if you wouldn't mind from straight back, and the side with full throttle

 

sounds kinda quiet compared to mine, i kept the stock resonator and mostly stock piping... (at the time i planning to upgrade in the future to bigger piping and an xpipe, just hasn't happened yet)

 

What is the a4 code that you're talking about, can I do that on a '98 A6 2.8 Q, and where can I find more info about it?

Thanks.