Ok, here's my situation. I have a 00 TA, Manual, and the only mod I had done to my car was the loudmouth exhaust. I was debating on LT's with an offroad Y but everyone says the sound is just too raspy with no cats so I thought I would remove them just to see what it would sound like. Well you guys were right, Sounds great when it's being floored or at idle but when you let off the gas it's like a dump truck, almost unbearable. What really has me bothered is the fact the car feels a lot slower. Before the cats were removed the car would get totally nuts when trying to take off from a stop. It would spin all the way through first and at least halfway through second. Now it will spin halfway through first and basically chirp the tires in second. Top end it doesn't seem much faster but maybe it is, hard to tell. So my question is, Do you loose that much bottom end hp to gain it towards the top end?? I do know I have pretty good leak on the drivers side between the manifold and the cat delete pipe I put on There is three bolt flange and I broke two of the bolts trying to take the cats off so there is only one bolt holding the new pipe on. Would the leak be killing the hp?? I only drove it for a few hours last night and I noticed it was sucking the gas down pretty bad. I took the rear O2's completely off so the check engine light is on but I've heard that shouldn't make a performance difference. I guess I didn't expect the car to perform this way, but if this is the way it's going to be the cats are going to go right back on. Any imput would be greatly appreciated. Thanks

 

First, fix the exhaust leak. It's not unusual to see that happen after headers install with no cats. Drive the car and the PCM will start to learn and adapt then you will see the performance come back.

 

O2's can affect tuning a lot. if you don't plan on running cat's your better off getting the rear O2's deleted from the computer

 

I thought the rear O2's had nothing to do with the way the motor runs?? I'm fixing the leak today, I just hope the performance comes back. Thanks for the imput

 

The rear o2 doesn't impact the performance of the motor, it's main main purpose is to determine if the cats are in working order.

The reason you want to delete o2 from PCM is to get rid of that annoying SES code and to pass emission test.

 

I agree. It will not impact performance. I got my cats removed & lost no power & it ran fine. Only thing that happened was the SES light came on & the exhaust has a stronger odor.