I used to tune by ear until I bit the bullet and bought a tach. To test it I tuned by ear as usual and then took a tach reading. I then retuned using the tach and was shocked at the results! I got an extra 2100 rpm out of the engine and it ran more reliably. Apparently the tach see louder than I can hear! The extra rpm immediatly showed up int the higher speed takeoffs and the air speed went from ok to "wow!". The price of tachs has dropped in half over the last couple of years so its really worth while to get one now.[8D]