Poor Fuel Economy After Header Install

[12gauge]

93 K1500 5.7L 4X4
I HAVE INSTALLED HEDMAN HEADERS WITH COLLECTOR BACK DUAL EXHAUST. MY MPG WENT FROM BAD (12-15) TO TERRIBLE (7-8) WITH THE TAILGATE OFF. I BELIEVE I SHOULD HAVE HAD AN INCREASE NOT A DRAMATIC DECREASE. IT RUNS BETTER BUT EXHAUST SMELLS VERY RICH.
I WELDED IN A NEW O2 SENSOR AND RUN ONLY THRUSH MUFFLERS. I CHECKED THE TIMING AND SET IT TO 1 DEGREE ADVANCE.

CAN THE FUEL MIXTURE BE ADJUSTED THROUGH THE COMPUTER?
-DEALERSHIP WONT EVEN HOOK UP TO MY TRUCK BECAUSE NO CAT

WHERE COULD I FIND SOMETHING CAPABLE OF ADJUSTING MIXTURE SHORT OF REPLACING ENTIRE INTAKE SYSTEM?

IS THERE ANYTHING I'M NOT THINKING OF?

ANY SUGGESTIONS ARE GREATLY APPRECIATED.

THANKS
-12 ga

[USN Jim]

12gauge, You need to reprogram your computer for your mods. then you will see and feel a differents. Summit,Jegs, and performance products has what you need. Performance products has alot for Silverados.
Hope this Helps, Jim

[juma33]

programming won't hurt but this sounds more like you have a leak at the exhaust manifold gasket or somewhere else downstream. the leak is feeding in oxygen which is read as lean condition and the computer is adding more fuel and trying to run richer. usually, with headers you end up running lean for a few hours till the computer adjusts and this is within the self-adjustment of the computer.

or maybe some vacuum line has been left off the intake??

its sounds like much to drastic a change to be something that won't require repair.

juma

[12gauge]

THANKS GUYS,
UNFORTUNATELY I HAVE A 93 AND "THEY" DONT SELL TO MUCH AS FAR AS REPROGRAMMING, ESPECIALLY IN A REASONABLE PRICE RANGE.
JET MAKES A STAGE 2 MOD THAT IS SUPPOSED TO HELP TRUCKS THAT HAVE HEADERS AND DUALS AS I TAKES INTO ACCOUNT THE LOSS OF BACK PRESSURE BUT IT DOESNT SAY ANYTHING ABOUT MILAGE GAINS.

I DONT BELIEVE THAT THE MANIFOLD GASKET LEAKS HOWEVER I WILL RETORQUE THE BOLTS AT THE MANIFOLD AND THE COLLECTORS.

I HOPE THIS HELPS. AS I TRY THIS, ANY OTHER HELP IS SURELY NEEDED.

THANKS AGAIN
-12 ga

[MrEleven]

I am not a mechanic by trade...but backyarders like myself say to unhook the battery, then reattach and see what happens. also i would run it hard for a couple of hours and see if you make it to a gas station. sometimes things are simple.