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Discussion Starter #1 (Edited)
Quick recap about a month ago I was doing trans testing on the dyno and noticed after I was done my HP was down to 510 whp after just making 539 whp in looking at the logs it seemed that I had just moved down in the octane map. Made a post in the tuning section and found I should set my low oct map the same or a lot closer to the high so knock does not have such radical adj in timing. I will admit my trans tuning was a little abusive :). At that point the car was off the dyno. Then not to long after I noticed the rear deferential wine. Loaded the stock Trans and Motor tune and took off my intake. Left mid pipe and 2.5 pulley. Took her in for Warranty on the rear end.

So fast forward to now. Rear diff has been changed did about 500mi of light driving. Decided I was ready to play again. 1st I put her on the dyno with stock tune and just the 2.5 and mid pipe. Just to see what it would do. I was guessing around 500whp but she only did 479whp. I put the intake and the 539whp tune back on. Only did 482whp WTF:mad: In looking at the boost graph I noticed I was a good 2psi higher then before. Which made me think choked up exhaust. I have already deleted the mid cats. So tonight I pulled the front cats down. Wow those bolts at the headers were stuck and of course on broke :(. In looking at the cats both seem fine. No melted front areas like I have seen before. I am going to build a delete tomorrow to rule them out, but my hopes are not high at the moment. Has anyone ever seen something break in the mufflers or have any ideas for other things to check?
 

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sorry I cant help, I would have thought some one would see this and have an idea. Bump for this guy
 

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Discussion Starter #3
We will find out if it is the cats or not tomorrow. I am absolutely flabbergasted at how much louder the car is with the Front cat Delete with stock headers.

So at this point I am a true 3in from Stock headers to Stock mufflers. Prying this fixes my hp problem and adds a few hp.
 

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Good luck. Let us know how it turns out
 

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I am having similar issues but I do have a slipping clutch. That is likely where the issue lies but I decided to inspect my hi-flow cats last night anyways. They seem fine for the moment though I plan on removing them for peace of mind. This car is UNREAL with open headers holy shit.
 

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Discussion Starter #7
Yes IAT's are good. 70-90deg 1st 110-120 2nd. Only having a 2.5 upper I should not be chasing the temps yet :)

The Cats did the Job for sure she is back up to 535whp at almost 1 psi less boost then before the cat problem and 2-3 psi Less then when the cat were not flowing like they should.
 

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Glad you figured out the problem. How do you like the sound of the car without cats? Sound clip? I love the sound of a car with no cats, but hate the hint of gas smell.
 

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Is this a normal thing for cats to get clogged up?
 

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We will find out if it is the cats or not tomorrow. I am absolutely flabbergasted at how much louder the car is with the Front cat Delete with stock headers.

So at this point I am a true 3in from Stock headers to Stock mufflers. Prying this fixes my hp problem and adds a few hp.
Sound clip of this exhaust please......

Sent from my KFTT using Tapatalk 2
 

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Discussion Starter #11
I will try and get the clip up tomorrow.

Not really liking what almost sounds like a exhaust leak but its a light tinny sound and its not a leak. I think I may rebuild my little cat deletes with some small straight though mufflers.
 

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Cats become an issue with serious hp. I fought to keep them and it was a mistake. I shoulda ditched them with my first round of mods.
 

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I will try and get the clip up tomorrow.

Not really liking what almost sounds like a exhaust leak but its a light tinny sound and its not a leak. I think I may rebuild my little cat deletes with some small straight though mufflers.
Really considering just doin stock manifolds with cat delete plus 2.5 " x pipe to remove crimped section to stock mufflers . Also remove rear resonators. Not planning on 700+ levels and still want my v to sound mild vs wild. Likely will never push more than 650

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