would removing one cat in front of the Y pipe make a difference or am i better off taking two out?

 

if you remove the smaller converter up front, pre-converter, you wont really notice much.

but if you run with just pre cats you will really know it!!

 

What he ^ said, but I will add... Don't take out only 1.

 

i agree..but i thought he meant 1 on each side..not just one of the 4

 

^ HA! I wasn't sure, but thought I would clarify. You never know...

 

I do believe he is asking to take 1 out of 4 out...please don't do that. Take 2 or 4 off.

 

^ agreed. you gotta take them out equally or the exhaust flow will be really un even and you dont want that

 

Take the cats out as a pair only, fronts out together, or rears out together. Removing only one will result in a odd tone, and a lean code.

 

if i take a pair out will it affect the back pressure or will i have to change anything with computers or will it be fine. 99 F150 5.4L

 

dont ever say anything about "back pressure" again!

on your '99 if you take out the front converters you will be fine, if you take out the back converters you may have to change the o2 bung and MAY risk running a CEL, which can be fixed by MIL eliminators, gotts o2 mod, or a tuner

 

back pressure...

 

ok so then if i take the front ones out and just replace them with a pipe should it be fine then?

 

If you take the front ones out (most toward the engine) then you will have a CEL and possibly experience fuel issues. The O2 sensors are downstream from the front cats and are designed to take readings from the exhaust after they have gone through those catalysts.

 

^ no you wont, not on a 97..i ran my 2002 that way for...about a year and never had any problems

EDIT:clarify..i had the front 2 converters cut off and left the bigger (rear) converters on

 

you will be fine taking out the front two smaller ones. i removed the two big rear ones on mine back in the fall and havent had a problem yet.