Did you work on anything else about that time?
Is there back pressure?

 

Deductive reasoning points to the headers. I can't give any first hand experience, but maybe you could post a picture or link of exactly which headers you bought.

If there is too little back pressure you can certainly lose a bunch of power in the low to mid range due to lowered exhaust gas velocity.

 

You're correct in thinking that the post cat sensors don't have anything to do with the way the engine runs; they simply measure catalyst efficiency for smog control purposes. Since you didn't mention doing it; I'd double check every vacuum line and electrical connection anywhere near where you were working. Unplug, check the pins, and replug all electrical connections, and make sure no vacuum lines got kinked/damaged/disconnected.

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If there is too little back pressure you can certainly lose a bunch of power in the low to mid range due to lowered exhaust gas velocity.

Correct on the velocity being important, but it still shouldn't be called back pressure. :thumbsup:

 

No nothing at all, just swap the headers.
About the back pressure im not sure how to notice it but i assume some noise.
The engine actually behaves fine, no strange sounds or anything else except the loss of power.

 

Here is the link to the headers on ebay....
http://www.ebay.de/itm/Facherkrumme...der-Baujahr-ab-1998-Edelstahl-/200959740618?pt=DE_Autoteile&hash=item2eca224aca

 

Short of a massive construction failure like something blocking a majority of one or more tubes, I don't think the headers themselves are the problem. I'd put money on it being something related to the installation like a sensor or something.

 

But nothing was found out when searching for fault codes, shouldn't it be seen when checking with the scan tool.

 

You could have reversed the O2 sensor connections, caused a vacuum leak, or have a huge exhaust leak.

When I drove around with open headers, the car was gutless.

 

I'm not really sure, just spit balling here but maybe limp mode from O2 sensor?

 

Did you reuse the old manifold gasket?

 

New gaskets were used.
I agree with Mr Tangent, i guess i have to check all the lines and connections again to see if something is bad there.

Could it be that i need to change the ecu programming now that i changed all these gadgets?
Or what about the MAF sensor, is there anything different between 328 and 330?

 

While a reprogramming would help you get the most out of the intake and headers, I don't think not doing that would cause the extreme power loss...

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Now that you have headers, where are the pre-cat sensors connected to?

 

Pre cat sensors are conected to first port on each header and post cat sensors to second port.

I just took the car for a hard ride and could actually hear a leakage from end gasket of header where it connects to the rest of the exhaust system.
It was only noticeable when pushing the car little harder, could this be the problem of such a dropp in power?

 

Its the Headers!

many years later I recently battled this issue. it is the headers and they are to free flowing. the car is tuned from OEM to have more back pressure, so it tricks the car into thinking that the throttle is wide open because of no back pressure and then cuts fuel from the car. you have to retune to no cat headers, put stock headers back on, or buy more expensive headers with cats for back pressure. i recently heard of a quick fix and thats and thats putting spark plug defoulers on the 02 sensors. the top set of 02 sensores measure temp and well as pressure.