Im looking to replace the 4 cats on my 5.4 with some hi flow cats or just remove the rear cats. Any pro/cons to doing this, wheres a good place to buy good brand high flow cats.
Thanks

 

If you remove your rear cats, you WILL have to buy some MIL eliminators to get rid of the "check engine" light. You can get them off ebay for less than $15. Be sure to get the 2 wire kind. I got mine from "thebestmileliminators" and they've worked great for months!

Now as for "should you?".... I would say no. I have your exact truck, and I saw NO gains in any way, except for a slightly deeper tone, and a very slight drone at 55mph. I see no point in ether removing your cats, or getting hi-flows. I removed mine because one was split, and a new set cost $1,100. No other reason, and no other gains. I would be happy to answer any other questions regarding the procedure, especially since we have the exact same truck.

 

you didnt notice any increase in mpg?

 

I noticed a slight increase (like 3mpg), however, it has all but vanished. My truck gets sucky gas mileage anyway (usually 11-13 mpg), and when it went to 15 mpg for a few tanks, I got really excited. In all fairness it's almost impossible to calculate 3 mpg of change with any accuracy, anyway. Especially doing what I do....

I guess my mpg has gone up a little though. It used to be nearly impossible for me to get 300 miles to the tank, now I reach it fairly easily.... I like to attribute it to the absence of cats. I wouldn't expect too much if you cut yours off though.....

I recently blew my alltime best gas mileage of 15 mpg away. My new alltime best is 16.8 mpg. I did this on a 600 mile trip with the cruise set on 61 mph the whole way. When I got to my destination, I calculated my average speed... It was around 56 or something...

 

I went to hi-flows from no cats and noticed a mid-range gain....

 

Me too. I may be getting about 1 1/2 mpg better, but too soon to tell.

 

What type and where did you get your highflow cats from

 

The first thing I did to my Nav was exhaust. Now, mine's a little more to the extreme than you'll go, but immediately after I logged 19MPG on a long trip. The previous best was about 15mpg. I have true dual unequalized 3 inch pipes flowing through two magnaflow high flow cats (actually they are jeep 6 cylinder cats) and flowmaster 40 series mufflers. I have since never seen that mileage again with all the other stuff I added, as a matter of a fact I get a little less than half that now at 9.1MPG. I did not however, have to use MIL eliminators. As long as you have the front cats removed, you shouldn't need the MIL eliminators.