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Discussion Starter · #1 ·
I haven't started diagnosing yet as this just happened... I think i know what the problem is but it won't hurt to get a second opinion.

Got my cats sliced off last night.

This morning, 1st and 2nd gear have now power what so ever.... my boost gauge confirms as even at WOT it won't go past 0 psi. It's feels like stock.

3rd gear onwards... power comes back and boost at WOT runs normal (about 13.5 psi).

While at the exhaust shop i noticed the guy used smaller diameter pipes (much smaller) after taking off the cats. When i asked him why he said that it would be better for fitment purposes.

Could this be causing the problem? or maybe an exhaust leak?

I didn't notice last night as i wasn't giving it much throttle. It was way too loud after getting the cats removed and just sounded horrible!!

All my mods are in my signature.

The only ones i haven't put in yet are the cams, oil separator and electric water pump. (was planning on putting them in this weekend)
 

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Discussion Starter · #3 ·
why would that only affect 1st and 2nd gear though??
 

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That doesn't make any sense lol
 

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May 08 ROTM
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0 psi in 1st and 2nd.. Not going to be an exhaust leak or exhaust pipe diameter problem. If anything, the smaller diameter would slow the cylinders release of exhaust pressure and you would see a rise in boost.
 

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Skirt Chasing Philanderer
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Im with E, I would say this has nothing to do with your exhaust... Although, I honestly have no clue whats wrong with it though.
 

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Discussion Starter · #8 ·
i had already spoken to Brenspeed about this before removing the cats.
They said i would not have any problems removing them. The o2 sensors are turned off in their tune.
 

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Do you have a tuner you can datalog with?

Have you looked under your hood real good make sure they didn't disconnect anything. I would get under there and check everything.

they were working around the tranny so I would check it out real good.
 

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I think you need a re-tune.

The cats gone is allowing less back-pressure / restriction.

All the rear O2 sensors do is tell the computer whether your cats are working or not.

As a general rule, you can change anything AFT of the cats with no re-tune, but changing cats or anything upstream (longtubes, shorties, etc.) requires a re-tune.

Get a custom dyno tune.
 

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Use the process of elimination...you did not have the problem before you had the cats cut off right? After the cats were taken off the problems started. Was anything else touched? if not then it has everything to do with your exhaust set up. A exhaust leak will not cause these problems at all, so I would then get the tune checked out. It sounds like your S/C isn't running right with your new exhaust setup and has something to do with your tune to me. Answer = a new custume tune is needed.
 
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