Hello everyone, spent Friday installing my headers. Initial impressions are very good, strong and more responsive than before and excellent off the line. Due to issues with the install and people refusing to do the work, dyno was not conducted. Overall only issues for me were access to some of the stock manifold bolt locations. No room what so ever even from below. The other issue was the length of the stock flex pipe. Once everything was installed and I cut the fron exhaust pipe right by the flex pie, it was still too long. I decided to just go ahead and get a new flex pipe and added a highflow cat. The pacemaker set up bolted right in though and fit nicely, no obstructions or space issues once installed.

Now when I initially planned on installing these headers I was under the impression based on my eletronic Diamante manual diagrams that there was a small cat on the rear bank of the exhaust manifold, well when I took off the fron bank heat shield, there was another small cat. Nowjere had I ever read about this additional cat.

Altogether this car has 1 main large cat and the 2 small pre cats located on the manifolds. To top it off we have a total of 4 O2 sensors 1 before and 1 after each of the small " pre cats" When I got the headers they did not have O2 sensor bungs, I received advice from a few folks to set the bungs at approximately the same locations as they were on the stock set up which I did. After I set everything up and looked at it, this piece of information hit me across the face as never before...

"What is the purpose of the O2 sensor and why are they before and after the cat converters?" To make a long story short, I realized that my O2 sensors in their current positions may not be giving my car accurate readings. In the next day or so I will see how the car behaves in extended driving, wether it will run rich as I think it will or wether resetting the ECU will actually adapt to the new flow readings.

Should I go ahead and relocate the two O2 sensors which originally after the small cats behind the main cat? This would involve extending the wiring but would this prevent any O2 sensor issues? If so, should they be staggered behind the cat since the really isn't all that much pipe right after the cat?

Any input would be greatly appreciated. :bowrofl:

sounds like the original set up was to measure the difference in O2 to detect whether the CAT is doing its job. so I have to agree with your thoughts, you should move the two front ones to the front of the CAT and two rear ones to the rear of the CAT, else your computer will probably give you a error code about your CAT, but probably shouldn't do much to the normal opperations, I hope.

Thanks WhiteDevil, that's what I'm considering doing. Just to the rear O2 sensors, this however will bring other issues. In adding wire to the length of the O2 sensor, it may change the electrical resistance then sending the worng voltage reading to my computer.

So either I way I may be screwed. BUT :D as of this morning no lights on and the power increase is very noticeable!!!

Hi there,

You don't happen to have purchased that car from California or live in California do you. Its
because the cars in California have much stricter (sp?) environmental laws and their cars must
be fitter with pre-cat cats as well as extra O2 sensors etc.

BY GEORGE I THINK WE'VE GOT IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :bouncin: :bowrofl: :D

I never thought about that particular factor in this set up. I purchased this car from a government auction, it was a vehicle seized by the FBI during an operation in California. That could explain why this particular car's exhaust layout did not match the diagram on my electronic service manual.

Man, you have honestly given me a whole new angle to research this. This will also bring up a concern for me. Not realizing this I replaced the O2 sensors but did not buy the California spec sensors, just the regular Bosch sensors. Wonder what could happen from that?? :confused:

Thanks for input though, it explains a lot for me now.

BY GEORGE I THINK WE'VE GOT IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :bouncin: :bowrofl: :D

I never thought about that particular factor in this set up. I purchased this car from a government auction, it was a vehicle seized by the FBI during an operation in California. That could explain why this particular car's exhaust layout did not match the diagram on my electronic service manual.

Man, you have honestly given me a whole new angle to research this. This will also bring up a concern for me. Not realizing this I replaced the O2 sensors but did not buy the California spec sensors, just the regular Bosch sensors. Wonder what could happen from that?? :confused:

Thanks for input though, it explains a lot for me now.
Thats ok. Last I heard is that California as strict reinforcement where exhaust emmisions are
concerned. Don't know if you know that there's a US Diamante forum as well with members
from California. The url is http://www.diamanteowners.com/forum/

I'm a member of that forum also, California emissions standards is just one of those little facts that no one thinks about you know. We tend to compare what we have versus what is available in Australia but forget that here California has it's own standards.


I can tell you from the few times I've been out there, the reason they're so strict is that terrible air quality. There are days, you can't even breath because air smog and conditions are so poor.