So many threads lots of great information here!

Here is my story. Several years ago I bought a used 2000 F150 4.2l 5 speed with 125k miles on it. Living in California and the cost of fuel eating my lunch an dinner I began to experiment!

1st I dropped the exhaust and punched out all 4 cat converters. It really seemed to open up the sound and increased my MPG greatly. In doing so I lost power. If you look at exhaust you see all 4 cats, they are just hollow.

The truck did throw some codes on the O2s. I took 4 spark plug fowlers and hollowed one out then attached 2 of them together (1 regular and 1 drilled) then I screwed them in to my exhaust where my O2 were and finally screwed the O2 in to the end fowler. Unplugged battery. Fired truck up and no more codes.

2nd I picked up a throttle body spacer off of ebay and a cold air intake. Yes I know its already cold air intake, but this one looks way much cooler! The spacer, may help I really dont know. But it sounds even better then before.
Still no power increase but an improvement on MPG still. I am getting 400 milles to a tank. Strangly when I take off easy it sounds like a diesel. GERR

3rd I found a steal on set of pull off tires and went to 265 75 16. It looks real nice! Fills in my fender wells perfectly and gave it a bit of a lift. As I expected my speedometer is off (5MPH after I hit 35. Not an issue for me.) Still getting close to 400 to a tank. I use a GPS that calculates millage and fuel purchases to get my MPG

Drove it like this for some time and decided to pull the spacer and CAI and go back stock. The truck still makes a diesel sound and is not real powerful on take off.

I noticed some rattling coming from my exhaust. I made a stop by my local muffler guy and had him take a look. He said that a baffle in my muffler had broken and that was the ruckus I was hearing. I explained to him all of the fun and exciting exhaust stuff I had done. He suggested installing a resonator, new muffler, and welding up the pipes.

$150 and I have much more power and not so much dieseling noise.

So now with a little more power and a sudden spunk of energy I would like to get more out of it. I just finished installing a complete front end kit, changed my manual transmission fluids, tune up, and put back on the throttle spacer and CIA. Still get the dieseling.

With the resonator, I have more power but its not what it can be.

My thoughts are:
Changing out rear end gears from 308 to 355 or a 373
Putting in a stage 2 clutch (still on factory clutch at 220K+ miles)
Installing an electric fan
Installing a new water pump
Installing a new timing chain and all of the goodies
Installing new belt
Picking up a tuner / programer and making a few mods

Now I know its a 2000 and its old, but it sill runs nice, looks good and I do not have any payment on it.

My questions:
355 or 373
electric fan vs fan clutch
what programmer can i get the most out of
Is any one in North Houston / Spring done this type of mods to their v6?

So that what I have. Suggest away please.

 

Electric fans gave me a solid 1mpg gain on my 4.6

 

Did you use a kit?

 

No I didnt, you can build your own kit for around 100 bucks if you know what you're doing

 

A tune would help. but, you have done so much to the intake and exhaust it would have to be a custom tune probably performed on a dyno.