vibrologist wrote:Get the proper plugs for this engine. The 2ZZ engine (GT) has higher compression and high octane requirements and this is one reason it has different plugs. It could possible a source for your idle issue.
The idle issue was before the plug change. I just changed them recently and I noticed that the part number on the plug was just slightly off from the one in the manual.
However, Since it is for the GT that runs higher octane, I believe if there is any real difference between the plugs, it is that the ones for the GT are slightly hotter burning than the base engine for the higher ignition temperatures of higher octane gas. The gap is the same and as long as the spark is hot enough to ignite the fuel it should not cause an issue.
The installed and recommended plugs are both DENSO Iridium so I will see if I notice a difference and if I do, ill spend another 30 bucks on new plugs.