So i removed my 2 rear cats and hollowed out the 2 front this past saturday, and i'm surprised i'm not to happy with it, nuber one it was a PITA to do, Number 2 If sounds sound all that great now with my flomaster 40 series mufler dual exhaust and number 3 my truck threw 2 codes at me after i did it code one bank one number 2 o2 sensor running lear and bank 2 number 2 o2 sencor running lean, i'm not to happy about this has anyone encountered this problme, i was hoping for a louder pitch sound, did i damage my o2 sensors when hollowing out, or should i just remove the 2 front cats and have them replaced with 2 high flow? btw my truck is a 2004 F150 screw 5.4
any help would be appreciated

 

I think you are better off removing all four cats and replacing with 2 magnaflow 94106s. That's what I'm doing and what most here do.

The codes are common when you remove/gut cats.

 

I removed my rear cats and havent had any problems(Knock on wood). Cause from the way darren explained it to me, on the 04, the rear cats are not sensored and the front 2 cats he said were just about the same as high flow cats.

 

If you do cat removal, you should have only cut off the rear 2. I'm not sure on why you gutted them because that is more harm than good. I would just get to a shop as soon as you can and get 2x 94106's welded in with the o2 sensors mounted behind in bungs.

 

Your mistake was messing with the front cats. If you had left them alone then you would have had free hi-flow cats basically. Now you need to replace them with 2 aftermarket hi-flow cats. The pre-cats are a small catalyst with no resonation.

 

Correct

 

yeah but i do not want my truck running lean, just cause the codes come on does that mean that my truck is now running lean after i did that?

 

No your not, but you are running gutless since you aren't tuned to run without cats. The CEL is just the ECM telling you theres an error with the cats.

 

well now for my stupid mistake, what is the best hi flow cat i can put on my truck if i have to buy new ones now i mine as well go witht the best?

 

Magnaflow #94106 cats from Performance Peddler, $94 shipped with coupon code 'clubgp' and the rear O2s mounted after the new cats. Good to go afterwards.

 

or should i just reaplace the 2 front with oem?

 

both of them shipped for 94$?

 

With that coupon code yes, otherwise $126.00 shipped.

 

ok thats good i will order them this friday, do they come with new 02 sensors on them or do i need to buy new ones?

 

This could have been prevented...