i've been having a couple of issues with car since i replaced my entire intake/exhaust.

#1 first header was defective (pin hole in the collector). $180 labor.
#2 i lost a crawford cat (right side) due to the stress from the exhaust. $70 labor (doug covered the cat under warranty).
#3 lost crawford cat (left side) collapsed (most likely due to the 02 sensor before cat not being threaded in all the way). $250 parts, $70 labor.
#4 which then leads to an 02 sensor needing to be replaced ($160)
#5 side note - ur pulley worked great, but gates belts would not stop squealing (even the second set). so i went back to stock on that also. $160 labor.

so after all of this, i decide to return my headers, cats, and pulley back to stock. $848 later (including gaskets), and my engine purrs like it used to, no rasp of any kind. but damn it is slow! it feels like my car has serious lag. my wife even said, 'damn! what happened?'
i'm still running an aem cai, kinetix plenum, y-pipe, coned into a modified mid-pipe, and a blitz rear.
she's headed back to mostly stock (until the supercharger goes on, most likely stillen, so i needed to do this stuff anyway).
i took for granted that people say exhaust doesn't net much gains. my dumbass believed them, so i didn't dyno. but now i'm pissed that i didn't. it feels like my car is loaded down by an additional 400lbs. i wish i knew what happened.
i ran a 13.96 with my auto sedan, with all of that crap on it. i'd like to compare it to what i have now.

has anybody else done this?

 

Not certain why you expected anything different; headers and hfcs do make a good difference...... the problem is people say, for example, headers are 'useless' because they don't give +60RWhp like they do on a V10 Viper.

 

you're right... i think i'm just pissed off and needed to vent.
i just hate how slow it seems right now. maybe i should get rid of my 19's and my 12" subs and get my power back.

 

Keep in mind that noise and vibration contribute greatly to a sensation of speed. My old 96 Maxima 5MT (14.3-14.4s) felt FAR faster than my G35 sedan auto. The Maxima was louder, had more vibrations, and lacked the refinement of the G35. My G felt like a 14.7-14.8 car. It ran 14.3s with a z-pipe and is .08 seconds quicker than my fairly modded old Maxima. That proved to just how misleading noise and vibration really is.

Headers have shown a consistent 5-8whp gain and "cats" haven't shown any real measurable gains. I highly doubt your car is much slower. Why not go back out and make some runs at the same track and most importantly, under the same conditions?

 

Wow man, I never knew you dipped into the 13's. Quite nice. Sorry for the OT post.

 

????????????????/

 

daveb - i know that my perception of power is influenced by sound. but really. my car still has quite a growl from the y-pipe, modded midpipe, and rear that still sounds quite nice. but this 'lag' is so noticable, it's pathetic. i'm talking about down low, 1500 - 3000 rpms, where full song is not on yet. she doesn't want to move. i never knew how much those mods actually helped until they were removed, and now i'm regretting it (a little).

 

maybe I missed it but did you reset the ecu?

 

I was thinking same thing

 

After removing all my mods in my sig before selling my car, my G35 felt extremly slow. And this is no noise sensation like some people might think. The car use to lay me back in the seat hard and now it doesn't even do it anymore.

Certain mods gain a lot of power on the G35 if you do it right. And you most of the time don't notice the huge gains until you actually remove the mods. You notice a loss more than a gain usually.

 

Where is your experience that he supposely lost no power? Please provide us with this data.

 

I never said he didn't loose any power. However, the gains of the mods he removed are pretty minimal after reading through the hordes of dynos on this site and 350driver.

Let's see:

UDP - maybe 2-3whp if you're lucky
headers - 5-8whp
Cats - nothing really

Overall, he probably lost a whopping 5-11whp. Hardly enough to take a 13.9-second G and put it in the mid to upper 14s

Like I said, why not take it back to the track just to see how much slower the car really is? Butt dyno = worthless

 

 

That's not all thats worthless.

 

daveb - i agree butt dyno isn't all that accurate... that's most of my frustration - the fact that i didn't dyno it, and i don't know what happened (when i put them on, as well as take them off). that's why i'm seeking other input - like g35_tx.