Okay, ~ 4 weeks ago I put on a Magnaflow 15609 cat back system on my truck, installed at a shop. A week later I put on Airaid CAI myself. I have had no engine problems or code but I have lost 3mpg over my stock setup with my same driving habits. Every thing I read said this would help with power and fuel economy. The truck performs great and there seems to be a real power gain overall. I just can't believe that my milage would be this dramatically affected. Anyone have similar findings or thought?

 

Wow, that's not good or what you should expect from that set-up. I put on a Borla SI/SO about a week and a half before the AF1 intake and with the cat-back alone I gained 1.8 mpg highway. The cai hasn't seemed to make any difference at all in my mileage. I don't even consider or worry about city mileage, it's gonna be bad no matter what.
Now are you SURE you haven't been planting that right foot just to enjoy the sounds?? j/k, wouldn't make a 3 mpg difference anyway to punch it every now and then.
Not sure what would cause such a loss just from your mods, it shouldn't.

Hopefully wiser heads will chime in here..

 

I'm sure your foot is in it more! Even tho you might not think it is, it really is I went threw the same thing with one of my 1st trucks then i went on a trip and made sure i drove the way i used too b4 the intake and catback and i picked up 5mpg on trip Se when you got the sound from the intake and catback you like to hear it more so you will like to take off a little faster or Punch it every now and then even tho you dont no your doing it!

 

When you installed this system. Did you disconnect the battery. Theres a little trick that people dont know about. But what I tell people to do is disconnect the battery and turn on the Headlights. What this does is it clears any memory from the computer and do this for about an hour. Then hook up the battery. This should help out your issue.

 

I had the battery disconnected but not the headlights on, so I tried that last week here while cleaning up the posts. Still waiting to see how it affected it.

 

resetting your computer for an exahust/intake wont make a difference. You cant tell us you didnt get on it at all while testing your mpg...?

 

Well that will usually work in most cases.

 

Ive have heard to disconnect the battery and reset the computer. But i can gurantee that you were flooring it to hear that sweet sweet sound of exhaust....

 

Well after my 2nd tank of gas and putting my foot into it I came out with about 15.4 mpg. I had also added the sock that goes over the filter as a prefilter.

 

Talked to a local shop that handles after market parts. They told me that the MAF is extremely sensitive. What I think has happened is when I put the new CAI in I took my canned air that I use to clean my computer guts and quickly gave the MAF a dusting off. They tell me that has left a residue on the MAF and thats why my fuel has gotten worse. So I bought some MAF cleaner and I'm going to try that and see what it gets me.

 

Well I tried some fuel conditioner recommended by a garage I deal with and on my last tank of gas ALL city driving I got

14.38 miles per US gallon
17.27 miles per Imperial gallon

 

If you did shoot the MAF sensor with something, there very well could have been some kind of a residue left on the sensor. Here in the states at the local auto parts store they sell a special MAF cleaner made by CRC. If you can find that or something similar that is made to clean the MAF you could try that.