I've decided to buy 2 hi-flow cats to replace my rear cats with. Since No shops here will convert me to a two cat setup, i'm on the fence on these two cats.

94006 is a 12" body hi flow magnaflow cat thats 2.5" and is commonly used with the 4 to 2 cat replacements.

94106 is a shorter body 94006, its a 9" body.

Now the question, there is no sensor after the rear cat so I should have no problems. Since i'm leaving the pre-cats alone and looking for sound, am I better off going with the 94106s? I'm 65% positive for those but i'm still uncomfortable to buy, Car-Sound themselves said hi-flows wont make a sound increase ( b/s ) and they only use 94006s. Would like to hear feedback from anyone who has done a rear cat only replacement please!

I got 2.5" true duals with Magnaflow 11" body mufflers, love it but just want it a hair louder. Thanks.

 

Just cut your rear cats off. save money and make it louder.

If you absolutely want to replace them, go with the smaller ones for sure. Spending all that money, you best get the most sound out of it since thats the reason for doing it.

 

I prefer 90210

 

The only thing keeping me from doing this is will my computer be damaged from this? and I wanna be careful about that $10k fine.

 

I agree, that 10k fine would suck. I just can't understand spending another 300-400 bucks just to replace the rear cats...i doubt it'll get that much louder or even free up airflow since the front cats are still there.

I'd just get custom tunes with the money. Or spend it on headers, that'll increase sound big time.

 

Do they do a sniffer test up there?? Either way magnaflow has some CARB EO certified high flows that are legal everywhere. If you just have to pass a obdII test the high flows are "supposed" to clean up the exhaust enough not to set the MIL. Chop the 4 off, put two high flows on and go with it. I don't know exactly what sound you are looking for, but the similar setups to yours I have heard with high flows did not sound good to me at all.

 

my friend cut his 2 rears off and welding in tubing....i dont know if it still passes emissions or not. could i do this on a 2000? without throwing codes

 

Well if it wont hurt my computer in the long run ( 10k or so miles from here ) i'll try deleting the rears. But until I get a guarantee it wont hurt it then I wont. If I dont get a guarantee what I can do is have the hi-flow cats inplace of the rears, and have my pre-cats cleared out and straight piped for $200 by a shop. That will cost a f'n lot, so I want to avoid that route.


No sniffer. I dont have emissions, just the visual inspection. I cant remove all 4 and replace with the two, I want to, but no shops will do it, so i'm screwed with the 4 unless I trade it for an '06+. I want my exhaust sound as it is, just volumed up alot more.


'97 - '03 rear cats are like my pre-cats, they do the serious work and control the CEL part, so no, but your pre-cats can be gutted and no code thrown.

 

If you want the sound,,^^^then this sounds like the only way for you to go.

Cutting off the back 2 cats and putting in the high flows is not going to make enough difference to be worth the money you spent on the cats and install.
I think it will sound very close to the same as it is!

Phil

 

Yeah I guess your right on that. Well I all I could do is hoped for it Still considering chopping the rears temporarilly. But I guess i'm stuck to having 1 set gutted and hi flows installed, or buy the 4 hi-flow cat system.

 

As a certified Ford Tech I'll tell you it won't hurt anything, the 05 up only have 2, and its the same powerplant. Surely one of your buddies has a sawzaw and a welder, do it yourself, and just replace with the 2 high flows.

 

Thats exactly what I wanted to hear. Thanks! I'll attempt it. Shops keep tellimg me my computer will be damaged in the long run if I run just the pre-cats.

 

well ive done some askin around and pretty sure as long as you have some sort of converter on there you wont have to worry about a fine...my 2 cats are gutted and im not even close to an emissions county so all we have is a visual check (and most places dont even do that) but your computer shouldnt be hurt as long as you have cats between the sensors and as mac4.6 said and i would do the same thing (and i know no shops will do it for you not sure why but hey who knows) i would cut all 4 (somehow) and just replace the 2 you need with hi flows if your worried about the heat thing might just have to go with the 12" bodys instead of the 9" i think theres no real point in 4 cats on a truck i understand your takin care of your truck and i dont blame you at all...but if you take the 2 rear cats off and replace them with hi flows imo your just wastin money id rather see you replace the cats you need with hi flows and no rear cats or just cut the rear cats and leave the factory cats on however you can and i agree with sawin them off and buying about 3' of 2.5" straight pipe and welding it on yourself

 

will cutting out my rear 2 cats hurt my 2000? or should i be fine? would a shop do this?

 

ok heres how it is..ive got a 2002 which is just like yours if you cut the rear cats your check engine light WILL come on but if you cut the first 2 (pre cats) and leave the rear cats youll be fine i cut the pre cats and my light stayed off...then i cut the rear 2 off and the light came on so basically yes if you care about your truck then dont cut the rear cats off cuz its not really a good thing..but if you dont give a crap then go ahead cut all 4 but i wouldnt advise it yes yes yes all my trucks have had the cats removed soon as i could get to it...but if you like your truck then leave them on but cut the pre cats