Just swaped out my NGK iridiums for some 3 range cooler autolite race plugs. The car seems to idle a lot smoother. Not sure if i gained too much on the HP or KR side from just these but I switched back to my 3.4 pulley from the 3.2 (exhaust restrictions are killing me) and my KR almost totally went away. I'm still seeing about .3 to .4 KR at wot in 2nd gear, but thats much better than the 4 to 6 KR i was getting. Gotta save up for the headers now and some exhaust work.

Thats a great improvement. What part number are you using?

Those are the plugs we run in the GTP. (Autolite 103) They didn't make any noticable difference from the AC-Delco 41-919'* that were in there, but I would assume that is because the car was getting 0kr with the 919'*, so there isn't any reason why they would give an advantage. From what I have experienced so far with them, they seem to be good plugs. I just think its stupid to change your plugs 10 times more often than you really need to.

Shawn

Autolite 103R i think is the number. The race version of the plug has the upper electrode filed down so that it ends just over halfway of the bottom electrode. The plug will wear much quicker than the iridium plug but i think the TR551X was just running to hot in my engine.