Here is a screen shot of a portion of the Zeitronix log of RPM and AFR showing a 3rd gear WOT pull this am. The rpm trace is quite smooth and similar to the ones from the tach output of the old MSD box.
I made one modification to the circuit, adding a 470 mFd capacitor between pins 1 and 8 of the 555 chip.
76 Suzuki GT500
2011 Jaguar XKR
A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke