Have an older RV-4 with unfiltered ram air set up. Has a step or stutter as you advance RPM. Slow throttle advance stutter is passing through 1200 RPM, Fast throttle advance stutter is at 900 RPM. Original carb was just replaced with a rebuilt by my local IA and I. It had leakage issues. Both Carbs have had this stutter during throttle advance. The new carb is a bit better, but still has the stutter. IA and I have checked for induction and exhaust leaks. All seems fine. Has any one else noticed this with the unfiltered ram air set up?