I need to rule the headers out. Ever since I did the 3.4 swap, my mileage has dropped a lot. I'm getting about 90 miles less per tank. (360 avg down to about 270)

I changed the o2 sensor Sunday when I was still on the full mark, but I still reached empty today way too soon.

I'm wondering about the injectors though too. Dumped some injector cleaner in the tank last week, but it still sucked gas all week. Maybe it's something injector cleaner won't fix. I'll start another thread about all that.

Anyway, how have the headers worked for you?

 

for me Ive seenan improvemnt in gas milage takes longer to get to E now.

 

i didnt notice any drop or gain really in gas mileage. if you lost that much, theres something else going on. i noticed a big drop once i put in a new cam/did a mild port on the heads and lower intake/ deleted the heater/ deleted the egr/ a few other things. im not sure what contributed to the most loss, but not headers.

 

Well I guess I'll look into new injectors or double check other fuel system stuff.

 

Could run some seafoam in there. Really big in the bike world. One of the very few products that actualy work. Most run 1/2 a can to 3-5 gallons.

So many funky running problems have been fixed by running a can through.

can be found at napa n others.

also big i nthe subaru board for cleaning out sticky lifters.
Product says n oil n gas on the can.

Its from the marine world and I dunno how but it does work where others don't.

 

I found it at Auto Zone.

 

I dont think I noticed a drop. However, I am going thru 02 sensors like crazy. So when my mpg starts to drop, I replace it and fixed.

What else did you do besides install 3.4?

Check to see if your loosing fuel pressure after turning the car off.