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.

Any suggestions?

Try putting a longer pressure line on that's like say 3" longer.

What effect does a longer or shorter pressure line have? Does a longer line equal less pressure therefore a slightly leaner condition?

The longer line has a little delay in it, dealy meaning takes longer for exhaust pressure to flow thru line into take and that makes midrange lean out a little b/c there isn'e excess of fuel pushed into the engine. I feel shorter line is more responsive and usually can give more problems for like idle quality or reliability over a longer line.