Well I tried the sled out with the little bit of snow we had and i got a problem. D&D suggested 390-420 mains for the single that i put on then I went up another 3sizes for the K&N filters. So i'm running 450s. What happens is for about 30 secs it runs great after letting it warm up. Then it boggs out and won't go above about 7000rpm and no snap. It will come out of it for a few secs at a time. If I let it cool down it still does it, tell it sits for a half hour or so. The plug color is a nice brownish tan color and the egt temps(don't know how acurate yet, but are around 700 at the high). I had a bad tank of gas last spring and this summer had to clean the carbs which had a green slime in them. I emptied the tank completely and replaced the filter. Also it seems really rich at idle. Any suggestions or ideas would be greatly appreciated.