Need opinions about exhaust affecting mpg

[topless]

I have a '98 Explorer AWD with the 5.0 motor. I've searched and read about all kinds of exhaust systems and such. But, I have not seen anyone do what I want to do.
BTW, someone was on drugs when they designed this exhaust system.

Anyway, as I studied this exhaust, it has all the O2 sensors between the motor and a flange just upstream from the second set of cats. Since the exhaust is a single pipe there, I was going to have the shop remove the pipe from that flange and replace it with a 2-1/4 or 2-1/2" single, new muffler and run it out the back. In this process I lose the retarded "Y" to the second set of cats, the 2 into 1 muffler, and resonator.
By doing this, will it help with gas mileage or just make more noise?
Also, the shop said it might set an engine warning light, even though the O2 sensors are intact?

 

[aldive]

A properly designed cat back exhaust system can indeedhelp with gas mileage if you keep the foot out of it.

 

[AMMO_HOOAH]

You might or might not set off a CEL for the o2 sensor. I knocked my out years ago, and initially had a CEL for like 6 months that eventually just disappeared lol.

 

[topless]

I ended up with a Magnaflow dual in, single out into a 2-1/2" pipe. It has to flow better than the stock muffler-resonator into 2-1/4".
At least it sounds like there is a motor in it now.
It's 100% legal, since all 4 cats are in place. What a stupid exhaust design.

 

[BigODave]

A properly designed cat back exhaust system can indeedhelp with gas mileage if you keep the foot out of it.

He's right! I installed a Dynomax cat back system on my Ex and did observe a fuel mileage increase - approximately 1mpg on the highway.

 

[kert0307]

Some TM headers will help you out a lot too, since you have the 5.0

 

[topless]

Update. 2 tanks of gas, city average has hand calculated to 15.8 and 15.9 which is up from 14.2 on the tank before exhaust change.
I'd like headers, but can't justify $600 and the temptation to lose all the kitties would be more than I could stand.

 

[shadowless127]

Update. 2 tanks of gas, city average has hand calculated to 15.8 and 15.9 which is up from 14.2 on the tank before exhaust change.
I'd like headers, but can't justify $600 and the temptation to lose all the kitties would be more than I could stand.

You can always sacrifice a bit of performance and get the FMS Headers for half the price.... That's what I'm prolly going to do since I too can't justify $600 header purchase.

Also, have you upgraded to a Cold Air Intake yet?

 

[topless]

No cold air intake. Does it make that much difference? FMS= Ford Motor Sport? I didn't know there were more than 1 kind of headers available.