I'm looking for a way to adjust the midrange performance on an engine without a midrange needle on the carb. I have a Sirio TX 18 that runs great on the bottom and top but it hangs-up for a second sometimes coming out of sweeping turn right before it gets on the pipe. The engine runs great most of the time, it's just this one little area where it won't rev for a second. The engine is basically stock except I am running the turbo head and I shimmed the head down to about .025" (took the thick shim out, left the thin one in). The engine runs much better without the shim and the temps are much more consistant.