I dont think anyone else has really done this before so here goes. I would be honored if the mods would make this a sticky. I tried to be as thorough and articulate as possible.

Tools Used:

22mm O2 sensor socket
1/2" Breaker bar
1/2" Ratchet
14mm non-deep socket
10mm deep socket ( Only for engine cover and ECM cover)
6" extension
PB Blaster (loosen O2 sensors)
Plastic ramps from Wally World
Soldering iron
Fine electronic solder
Electrical tape

 

My CarsonTuned strut bar, engine cover, and SRT intake have been removed. Strut bolts are 14mm and the engine cover takes a 10mm.

 

Here's a picture of the bottom of the header where it interfaces with the stock Y-Pipe. There are three 14mm bolts that were fairly easy to remove. The two arrows on the outside point to bolts you cannot see in this picture.

 

Eight 14mm bolts to remove the header. They are also fairly easy with a breaker bar. No real struggle here. And yes, the header pulls out through the engine bay!!!

 

Before I removed the header I attempted to remove the O2 sensors which resulted in breaking a O2 sensor socket. Then, I went back to a different parts store to get another one and after returning I was still unable to get the sensor off. So I tried cranking the car and letting it run to warm it up which was suggested by a few websites after I did a google search for tips. Still didnt work even after acquiring some PB Blaster. I decided to go ahead and remove the header and just buy another O2 sensor that is before the cat.

Cranking the car with only the stock header hooked up to the exhaust sounds amazing. I will post a movie of what it sounds like with only the OBX when I get finished. I didnt even think about doing it with the stock header until it was too late.

 

Here is a comparison shot. My guess would be the stock header is about twice as heavy as the OBX. Weight savings are always welcome.

 

Here is a shot of the block with the header removed.

 

This is actually where I have stopped for the night. It is late and I need an O2 sensor to replace the one before the cat because it is impossible to remove. I will call LMS tomorrow and get the details on how to wire it in, per LXOGOOD's recommendation because, to my knowledge, he is the only other member with a header installed on the GS300. I have been in communication with him for a couple months about this install and he said LMS handled everything.

O2simulator.com does have a skimpy "guide" for an IS but, the diagram does not match what I see. I even had a fellow CL member "kurby" from the IS forums open his up for me and the connector was still different. Here is the link to the seemingly wrong IS diagram. No connector on either of ours under the cover has four rows of wires. We both have three.

 

Great stuff , thanks for sharing im also looking at the possibility of putting new headers on my 300 .

 

I called LMS today and they gave me alot more information. I discovered that they use the ALLDATA program which is quite common in automotive repair shops. I just so happen to fix the computers of a repair shop that has the ALLDATA program and I managed to snag this picture that I have updated a little to reflect the wiring job.

 

I called up LMS( Luxury Motor Works ) one day and the kindly referred me to O2simulator.com because the exact same sensor was cheaper. It is a single simulator but with dual outputs. Red and black wire are for power and ground. The white wires are the outputs.

 

1. Disconnect Negative Battery Terminal to avoid damaging vehicle electric system.
2. After removing the three 10mm bolts to the ECM cover, locate the required harnesses.
3. Solder O2 Simulator Ground wire (Black) to harness E3 position 17.
4. Solder O2 Simulator Power wire (Red) to harness E6 position 16.
5. Cut the E7 harness wires in position 25 and 26.
6. Solder O2 Simulator White wires to E7 harness wires 25 and 26.
7. Insulate wires with electrical tape and secure O2 Simulator out of the way.
8. Replace cover with three 10mm bolts and do your happy dance.


Should look like this when you are done.

 

The header hasnt been bolted up yet because Im still waiting on the O2 sensors but I wanted to share what it looked like.

 

I have the same header. But it's covered by LMS heatshield. YOu should consider getting one of those.

Intake tube directly under throttle body is a not good.

 

nice. thanks for sharing the info for the rest of us DIY'ers.