As I get closer to finalizing my MM tune, I was considering requesting an increase in idle speed. My idle occasionally shudders like most RX-8s, and I also have the AP Pulley, which reduces voltage at idle.

Will an increased idle smooth things out further, and if so, how much of an increase is ideal? I've read that beyond 900 can adversely effect the cat, but at the same time, how much does it need to be increased to make a difference? MM sets it to 830 by default, I was looking at between 850-900. Are there any side effects; increased fuel consumption, etc.?

 

Anyone have any comments on the technicalities here? Mysql said his was smooth at 900, and all was well.

 

I run mine at 920.
I've had some of the SC guys go all the way to 1100.
Its up to you.
The PCM will still play with the idle speed and mixture all the time no matter what. (Unless you want to completely disable closed-loop, which I don't recommend.)