One of the more advanced techs may chime in and I'm not positive but I think headers introduce more noise and cause false knock so u may be losing timing. Might need a lt4 knock module

 

how could i check that?

 

Scanmaster or some other dataloging method. Datamaster, freescan, etc.

 

The only way to determine if you are getting knock retard would be to hook up a scanner or scanning software, and observe the knock retard as the car it driven.

Are you sure you didn't burn a plug wire, or the O2 sensor harness wires with the headers?

Are you sure it isn't just psychological... the exhaust is making a lot more noise at lower RPM and lower throttle position, so you feel it's lost power? Have you actually made a pass to quantify the performance loss?

 

i am postive there is no burnt plugs or o2 sencer. and yes the car is louder but the car went from i could punch it from a 15 mph roll and it would spin from 1st to 2nd and stayy spinning untell it shifted 3d verry easy. i do that now and she spins a little and its like the motor is bogging down.

 

Sounds like the fuel is messed up.... and that often points to a problem with the O2 sensors/wiring.

Are your headers cera-metallic coated (e.g. "Jet Hot" or similar)? There is some evidence that the initial burn-off from the coating will damage the O2 sensors.

 

i coated the headers with black high temp paint with the header off the car.

 

how did you extend your o2 sensors?
did you buy extensions? splice into engine harness? splice into o2 harness? did you solder or just use crimp connectors?

 

all we did was splice into o2 harness with crimp conectors. like we just cut and extedned the stock 02 wires

 

Generally its more reliable to use ready-made extensions.

 

i bought the headers in a kit and that kit came with the wires and thats how the instructions said to do it

 

the o2 sensor wires are very very sensitive, might wanna invest in some preassembled extensions, they just plug right in.

 

I can verify that a Jet Hot coating will take out O2 sensors. I just had one throw a code. With info from here, I was prepared for it and it simply killed the old O2 sensors I installed in it.

 

This. I'm using high quality O2 extensions too. I recommend this as well.

 

I can tell you something that happened to my 1996 3.8 V6 Camaro back when I had it.

I bought some headers for it and never could get the collector flanges to stop burning up gaskets. I didn't keep them on the car long, but it did lose quite a bit if low end. When I put the stock manifolds back on the car, it felt like it picked up 50 hp. Sooo....one of two things was going on....the leaks were giving the O2's trouble or the reversion, that Injuneer described, was killing the low end.

I've just put long tubes on my Z28 and it didn't lose any low end and it really gained on the top end. My Z is a stock headed 350 engine with no port work(heads have been milled though...years ago due to warping by overheating), but does have a CC503 and 1.6 rockers.