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Discussion Starter #2
Oem headers have some interesting design features notice how the collector is designed to swirl exhaust out the primary tubes. The collector also has anti reversion built in.
 

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Discussion Starter #5
No silly questions! I think you get better flow with the smaller chamber and should make as much power as rpi/evolve setup 28rwp/28rwt. Before tune. My mechanic felt better about this setup then just gutting.
 

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They look great. for someone (me) who has not spent much time looking at factory headers what exactly is done?

is the cat section cut off the header and then a new pipe and v-band flange section added? or is that still the factory part and it's the post flange pieces that are new?
 

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is the cat section cut off the header and then a new pipe and v-band flange section added?
Correct. Its a clean setup and proven to make decent power. If emissions wasn't such a b*tch to pass I would consider them.
 

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I really want to get rid of my header cats and have been thinking about the best way.

I have no problem with the stock headers. they look like an excellent design to me. I just can't stand having a car with 4 cats, especially with 2 right at the headers. I'm used to cars with 1 cat or none.

I have seen some guys just try and break the cat cell up into pieces and remove from the headers with the headers still mounted. is it possible to cut off the cat section and weld in some pipe with headers on the car?

if I go to the labor expense of removing the headers to do it then I'm getting into the territory of probably just buying new headers...
 

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Correct. Its a clean setup and proven to make decent power. If emissions wasn't such a b*tch to pass I would consider them.


i have catless headers on mine. can't notice any improvement in power.

the sound is a little different thats all, not better, just different (actually i preferred the stock sound).

if i had my time back id definitely have saved 3-4k and not done it.

in these days where you can get 2-300 hp in tune and turbos from the new amgs and BMW's,

whats 20 whp??
 

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Discussion Starter #12
Headers are installed picked the up last week. I wanted to drive it a while to get a feel of the car. Slight change in the tone of the exhaust sharper is how I would describe it just a little more rasp out side no real change inside. Put abut 120 miles on it over the weekend. With miles the tone begin to change a little smoother closer to stock. Performance got better the more I drove it better response to the throttle in aii modes.

Took the car to frank smith to have a custom dyno tune on Tues. Frank tells me that a strong m5 puts down 380 to 390 on his dyno mine put down 411. After the tune the car kept getting stronger 430,433,437,440.
 

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Discussion Starter #13
Got back late tues was dead tired so I got up next day went for a ride. Oh s__t this thing pull a ton holiday traffic around town so I couldn't do a long pull. Went to bap geon picked up new air filters I ordered and put them in. Dam this thing running even better. Went by the shop to talk to my guy pulled out on broad st. and punch it "dam" broke traction all the way through 1st bang 2nd gear broke traction till I let up.
 

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Discussion Starter #15
Just an update with the m5 I've been having some issues with low fuel pressure under load and high rpm. Checked codes bad high pressure fuel pump. Replaced fuel pumps, fuel pressure switch, and mass airs.

Took the car back to frank smith weds night @ retuned it. It was running lean up top. We got fueling back to normal 12.7, 12.8. Before it put down 439 to the wheels. Last night it did 475.7 hp @ 378.8 ft/lbs to the wheels. On frank's dyno that's 570 hp @ 453 ft/lbs. at the crank not bad. He said after the ecu adapts should pick up another 10 hp or so. ?
 
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bemone
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