Will LT's solve the problem?
 

I keep getting a catalyst efficiency code. I filled my gas tank to see
how many miles I can get out of a full tank and I only got a 175 miles.
Is this a result of the catalyst problem? I also seem to have a lost of low end power. I ordered flowtech headers a month ago will these help?

How many miles did you used to get on a tank of gas? I have an A4 w/3.23's and I usually get 150 miles for the first 3/4 tank and less than 50 on the last quarter for a total of roughly 160-200 miles tops before I fill up again. I think I usually get 16 mpg at absolute best....... This is with in town driving with virtually no interstate and little highway and a lead foot. I realize it is running a little rich right now b/c of untuned headers and I get on it a lot because it sounds so nice but i've never got better mileage than that hardly anyway.

sounds to me like the cats are junk if it were me id ditch them and get an offroad pipe with those new headers

I dont remember how many miles I used to to get out of a tank of gas but I
know it was better than what I am getting now.

Yeah i would ditch those cats and get an ORY my 99 A4 W/3.23's got almost 300 miles to the tank when i drove it back from Texas I stopped one time for fuel in La. i think the average you should get is anywhere between 250-275 miles to a tankfull also be sure the fuel guage is working right they like to float :drive: hope this helps

99 A4 with 3.23s. other mods in sig. running really rich after headers without tuning.

i usually get 21-22 mpg (mixed interstate/city)
i got 20 mpg driving all interstate in 3rd gear (tranny problems)

i can get 300 miles on a tank easy and when the tank is entirely interstate,i have gotten 350+ miles. (24ish mpg)

I even get 18-19 romping it for a full tank

16 seems really low, you might wanna have that checked out