If they do, how much do they decrease MPG by?

 

I believe that a certain amount of backpressure is needed on the trucks to maintain temperature for the oxygen sensors and torque for the engine to run balanced. As per exact mileage it would be difficult for anyone to say for certain since driving habits, modifications, fuel quality, altitude, weather vary. But it usually is always in the couple of MPG. I don't think it would be drastic. :o

 

So crushing the inside of the cats isn't gonna be useful? That honeycombed ceramic **** inside?

 

the newer trucks have the computer expecting a certain amount of reduced flow from the cat, so by crushing it out you would confuse the computer which could actually hurt performance plus mpg cause it wouldn't have the expected backpressure

 

Well, damn.

 

All that is true if you dont fix your computer but if you do it runs great and picks up Mileage. I gutted my four cats on my mustang and it through a Ces light and it started running like crap and didn't get very good mileage and then I found this little thing that Plugs into your O2 sensors to fool your computer into thinking you got cats and it really picked up and run way better than it ever did. I had true duals no cats, with a H pipe flowmaster 40s. I also did the same thing except single in dual out on my 04 ranger 4.0 sohc. They will do the job if you dont have a programmer. They say its for a mustang but they plugged in also on my ranger. Knowing how ford never hardly changes things I would say these will work on our trucks. Im going to Gut the cats on my 05 4.6 f150 soon as summer comes. Right now I have a single in dual out with stock cats. Id like to go catless and true duals. Check this out, this is what I used to fix my problem. They are called MIL Eliminators I have found them cheaper other places but these are the nicest. Click on the BBK MIL Eliminators.
http://store.summitracing.com/defaul...=egnsearch.asp

 

I put an off-road h-pipe on my mustang - eliminated the cats. You will need a turner to turn off the cel light otherwise you will run extremly rich and fuel mileage will suffer drastically. Watch out...as this is illegal to do. Also without cats.....you will lose a lot of low end tourque.

 

What year stangs are yall talkin about? I removed them on my 89 and never got a light, didn't have to simulate the 02's, and ran 324HP NA with stock heads?!?

 

I had an 03 Mustang GT.

 

My Mustang was just a stock Gt 2001 mustang except cold air intake and the exhaust. I never ran into any of the problems you mentioned with that MIL. It did feel like it was running lean and not fully going wide open when I first gutted the cats with out the sensor plug. My check engine light also went off. Also as for loosing bottom end torque this is true a little but there is a plus side I gained a ton of mid to top end. Only thing I could notice when I gutted my cats even after I put the MIL on is that stinky exhaust smell. That got on my nerves more than anything. Pull up to a drive through and a gust of wind blowing from the rear of the car to the front it would blow all that crap in the car. On the ranger I couldn't smell it that bad unless I got right up close to it. Maybe difference between v8 to a v6 I don’t know just a guess.

 

I loved that smell....the smell of power