Z7What

As both things were said, put the cats back on. When i have my 2003s the largest gain in MPGs came from E-Fans.

Wayne

01-7700

I find that dumping all my old lawn mower gas in the tank improves calculated mileage (i don't account for the extra gas).

10thGenFnatic

Originally i cut off the cats because they were clogges and causing massive problems, cut it off and have the same mpg but have more power, i want to put good cats on it, but not break the bank, and i want it to sound good too have a nice rumble to it, what cats should i get for it with good sound and has o2 sensor port

white89gt

Look at the Carsound/Magnaflow cats. They are about the best you'll find to suit those needs. You do not need to replace the two cats closest to the motor, but the two rear cars need replaced to bring your truck back to sending your ECU the proper parameters it needs to run most efficient.

Usually if you've killed converters (clogged them) there is a reason. The On Board Diagnostics are usually quite good at telling you there is an issue that needs addressed. Was it driven for a long period of time with the Check Engine light on?

10thGenFnatic

the 2 cats closest to the motor are the ones i cut off, well i have precats then regular cats, and then after that it goes to a muffler and then out the back, i cut off the cats and gutted the precats
Im not sure what you mean by rear cats

white89gt

Think of where the front of the truck is and where the rear of the truck is. The cats closest to the muffler are the rears.

10thGenFnatic

i dont have 4 cats, i have 2 precats and then about 4 inches ahead of those i had regular cats, and then it goes straight to the muffler in the back

CoachJ

I think y'all are speaking in reverse lol. You're both kind of correct. Yes, there are four "cats." The two precats, then the regular cats behind those, leading to the muffler. The precats (fronts) can be cut out, but the rear cats do need to be there for your truck to be more efficient. Gutting them isn't sufficient. As mentioned above, look into some high-flow cats from Magnaflow or another brand.

jprevat

iTrader: (1)

Our trucks do not have "precats" we have four catalytic converters from the factory.

CoachJ

hmm...I seem to see a lot of pages calling them pre-cats and a lot of pages saying there are just four cats. It's been awhile since I've been in the 10th-gen scene, but they were always called "pre-cats" when I was pretty active in the 97-03 forums. I see nothing "official" calling them pre-cats though, so I assume you're correct. Sorry for the misinformation!