I have a 2000 f-150 with 4.10 gears,magnaflow si,so exhaust,k/n cai and troyer tuned x-cal 2 running 93 performance tune.I have 90000 miles on the truck and still on original plugs and o2 sensors,the truck is running fantastic though. I notice a rich exhaust smell and the mileage sucks[what f-150's doesn't]. My question is ,Do you think changeing the o2 sensors would help or could it be in the programming?, I never had it on a dyno.Any help would be greatlly appreciated. thanks

 

Even with program mods, the sensors are still in control of the fuel and should set codes if that rich.
Have you checked for codes?.
Going only by smell is not fully reliable.
A number of faults could cause worse fuel mileage.
Bad ECT, OX sensors, stuck open thermostat, bad fuel regulator, leaking injector/s.
These faults tend to show in other ways, as well.

 

No codes are showing, The truck is running fantastic,but i smell a rich exhaust smell. Do you think new upstream o2 sensors would help?

 

How many miles are on the O2 sensors on the truck? I believe, if I recall correctly, mike recommends changing them every 20K. My Nav runs exceptionally rich, set off codes indicating that, but during a dyno run using the livewire (or whatever SCT's software is) it reads perfectly fine. My states emissions laws seem to dictate otherwise. There are many reasons, but if you don't have a check engine light or seriuosly low mileage (and this is considering the state of your foot in the throttle) then you probably don't have a problem, just gas up at a different station

 

I have 90,000 miles on them! It has never thrown a code,The truck runs great ,But i smell a rich exhaust smell and i'm thinking it can't be good for my gas mileage or lack there of !?

 

change out the plugs.. likely cause of running rich. that or u could flush the injectors and seafoam the intake manifold. try using acetone to help the fuel burn more complete. less wasted fuel to blow out the pipe

 

Change the O2's, they've led a good life