My .074 runs like a top, and idles better than any other small motor I have. I have noticed that the high speed needle setting is very broad like you have said. This is a great characteristic. It does make me feel as if there could be some room to open up the carb for more performance. I won't do this because it runs just great as is, and I wouldn't want to ruin it. I have been making a bunch of turbo heads lately, and use a 1/4" centre drill because it has a 60 degree taper on it. My lathe (Hardinge chucker) is adjustable for the center size to get the .284" hole size needed. This solves the hassle of making a proper size form tool. I haven't done a head for the .074 yet because my plug is still fine. (touch wood) I'll try to remember what you said about being overcompressed and the rich idle. That would explain some things I have had problems with over the years.