I did not read the entire thread, so i do not know if anyone on here answered you question. I know the reason it does not idle right and how to fix it.

First of all many of the header manufacturers move the O2 bung down to the collector to get the most accurate reading from all cylinders. This causes the problems for none heated O2 sensors. The O2 sensor does not heat up properly and there for does not turn on, AKA thermal switch. So when the engine is warm the idle goes to hell.

The solution, Open up your AFM ( Air Flow Meter ) on top of the air filter box. You will need a razor-blade or equivalent. In side you will see a sprocket and a clamp holding the sprocket in place. loosen the clamp just a little. then turn the sprocket counter clockwise just three notches. Your yota will come to life and the idle issue will go away.

 

Does this richen or lean the mixture? We moved the bung to the header pipe and it started running like crap where it should have been more than hot enough.

 

it will lean the mix.

 

I will try that today. Last night, I returned everything to the original way we had it right after installing the header to try and isolate any mistakes. Unfortunately nothing got better. Brand new plugs, wires (including coil wire), cap and rotor and it sounds like shes only idling on 2 or three cylinders. Im wondering if adjusting the AFM will change that? Going to go try it now. I know I have the plug wires going to the right cylinders because I have checked it three or more times. I have adjusted the timing all over the place and it either speeds the motor up or slows it down, but does not smooth it out.

 

Changing the afm did improve the overall situation but it is still far from perfect. I am beginning to think that this has gone above and beyond my level of expertise. It seems like it is a timing issue, but I have double checked everything and adjusted everything, and nothing makes it work. I just pulled the spark plugs and they all looked the same...I dont know...I guess I opened pandora's box here.

 

Have you checked the vaccuum modulator valve there is a little filter under the little cover it may be clogged.

 

Pardon my ignorance but where exactly is that?

 

It is right by the intake manifold little round thing with 3 hoses atatched to the sides and one on the bottom its about 2" round here try this link . http://personal.utulsa.edu/~nathan-b...18egrsyste.pdf

it will show you. Good luck!

 

Took it to a mechanic...probably a valve or injector issue. Trying a can of seafoam in the tank to unstick the injectors. We did a heat test on the cylinders. Front two were 150 degrees hotter than the back two...

 

seafoam won't clean nearly as good as a bottle of techron.... the seafoam is better at cleaning out carbon in the engine instead

 

Seems to have helped though, smooth after 35 miles of hi revving driving...got the engine nice and hot (not overheated) and redlined her a couple times.