Should I remove the resonator AND the cat?

**dreama** · 09-11-2009

Hey guys, I was at my buddy's shop today, and he offered to replace my resonator and catalytic converter (99 GTP, stock) with a straight pipe for free////

---please provide your opinions, suggestions, and pros/cons....

THANK YOU!

p.s. - please respond quickly, as im going tomorrow morning (9 am)!!

**Planeboy18** · 09-11-2009

From what I've heard on this issue, your car will sound like crap, but will have a lot more pick up and a nicely throttle response, but the stock mufflers will sound funky. I don't know if this is true, but that's what I've heard. You might like the sound though, so it's worth a shot.

**blueguy** · 09-11-2009

If you remove the cat...that's fine. If you want your car to sound like ass take out the resonator.

Just get rid of the cat and u-bend.

**dreama** · 09-11-2009

so taking the resonator out will sound like ass?.....why do so many people do it

and do i have to have a u bend removal (ex: zzp part), or can they just remove the ubend and replace it with a pipe (what about o2 sensor?)

**stlmo_gtp** · 09-11-2009

i have my resonator out.. doesn't sound to bad does get raspy at time tho

**PolishedandWaxed** · 09-11-2009

yeh, gets raspy at like 3500rpms, idle and normal driving is fine though.

So if you replace the mufflers and with a deleted resonator it can sound better? what mufflers are recommended?

how do you delete the cat and keep the ses light off? I remember seeing a 02sensor thing that will keep the code off, is that correct?

**silverstreak** · 09-11-2009

I took my res off and had one put back on a week later. Sounds great at idle but when your cruising town at a steady speed the drone makes your car sound like a V6 with a broken exhaust. Thats my 0.02, everyone has different opinions about it.

**BoostedComp** · 09-11-2009

i dont even like the sound of these cars without a cat... i could only imagine loosing the res too... i would say def keep the resinator in... if you wanna kill the cat and delete the ubend with the straight pipe go for it. its your car... just remember without the cat you will be setting off an ses light unless you get the code tuned out
what i personally would do... just get rid of the ubend... and yes it can be done with a straight pipe... you dont need any special part from zzp

**Planeboy18** · 09-12-2009

You could go ahead and cut out the o2 threads thing and weld it onto a new straight pipe and save yourself the money. That was you could run the straight pipe with o2 and still get a little better flow through the exhaust. I think there's a writeup somewhere on this site about it, but I could be mistake. I'm still new here so...

**EmEaston24** · 09-12-2009

i never had a res in mine. it drones a good bit tho. i then again im not really sure what one with a resonator would sound like. but i plan on getting a resonator put back on sometime

**dreama** · 09-12-2009

would taking either of them off result in lower mpg? or higher? also, what would any tips be for u-bend delete 02 sensor placement

**MidnightSpecial** · 09-12-2009

I have a 3" Catless Downpipe and no resonator with the stock mufflers and it sounds very metallic at idle, almost like if you dropped a pop tab into an empty pop bottle and shook it a little bit. Also it sounds really raspy and crappy when you rev it. Keep the Resonator. Mine was gone when I got the car. I might even put in a cherry bomb one of these days to help with the raspyiness. If I want to be loud I can just click a button and my cutout opens. lol

P.S. If you do cut out the cat make sure to either get a 02 sensor simulator or retune your pcm because the rear 02 sensor DOES AFFECT THE FUEL TRIM!!!! I know most people on this forum thinks its only to let you know if your cat is good or not but I have a Service manual and it says right in it that the rear 02 sensor information fine tunes the fuel mixture. I will give you the page number and brand of the manual if anyone doesn't believe me.

**dreama** · 09-12-2009

alright, so i removed the u-bend AND the cat, left the resonator intact....and i gotta say the car sounds...well it sounds pretty frickin awesome! and considering it was a free job, im really happy...i also feel like the car got more powerful (u-bend delete?)...anyways, we removed the o2 sensor, and i was thinking of either getting a simulator (how much do they cost?) or just save up until I get either a FWI or CAI, then get an overkill or intense PCM....lemme know what you'd do!

**Planeboy18** · 09-12-2009

Originally Posted by dreama

alright, so i removed the u-bend AND the cat, left the resonator intact....and i gotta say the car sounds...well it sounds pretty frickin awesome! and considering it was a free job, im really happy...i also feel like the car got more powerful (u-bend delete?)...anyways, we removed the o2 sensor, and i was thinking of either getting a simulator (how much do they cost?) or just save up until I get either a FWI or CAI, then get an overkill or intense PCM....lemme know what you'd do!

Glad to hear everything worked out for you. I'm not really educated on this particular topic of removing the cat and rear o2, but my one friend, Kyle99GTP on this site, has no cat or rear o2, but runs a AEM wideband AF gauge and a PCM tune that has the rear o2 code deleted. If need be I can get you his contact information. He might be able to help you out with this a little more. I would say that getting the car adjusted to not having the cat and o2 would be the first order of business before a FWI or CAI, so I'd say PCM first then working about air intake.

**flash527** · 09-12-2009

You can get a O2 sensor simulator for pretty cheap, but if you're planning on getting a PCM anyway, just do that and have them program it to ignore the rear O2 sensor

**dreama** · 09-13-2009

here's the thing, i def. plan on getting a pcm, but if i get it before the air intake...im gonna have to program it AGAIN right? and i've been looking for an o2 simulator but i just cant find one (please provide a link!) in the meantime, are my mpg gonna drop?

**Bio248** · 09-13-2009

no, usually any off the shelf PCM is made for a bolt on car. they are usually set up to run best on a bolt on 3.4 setup.

**rynoman03** · 09-14-2009

I don't have a Cat, Resonator, or a Rear 02 and i love the way my car sounds. There is a little bit drone at certain RPM's though. I have a glass-pack for resonator but to get a full effect a person should go 20" or longer for a glass-pcak replacement.

You can turn the code for the O2 off with any tuner. HP or DHP.

Do it all!

And for what it's worth I have Magnaflow Stainless mufflers and i wouldn't change them for anything.

**MidnightSpecial** · 09-14-2009

rynoman03 - The only reason it does sound good with your setup is because of that Glasspack, Without it they sound like crap, seriously when I rev it there is an instant high pitched ricey-buzz-craptastic sound. I plan on welding in a 28" Glasspack where the resonator used to be and hopefully this will eliminate that sound. Nice GTP btw. Almost a older brother to mine. I have a almost brand new set of projector lights I'll sell ya for dirt cheap if your interested. They look sweet on a Black GP especially.