You are probably noticing the differences between streaming and block modes explained in my other response.
Pico 5 also streams but very, very slowly. So slowly as to be of no use for any but the slowest of signals. However, you can tell it to stay in block mode for better performance.
Pico 6 will switch between high speed streaming and block modes at the optimum time for your 3423 so no worries.
Tom Roberts
(The Picotologist) http://www.autonerdz.com
skype: autonerdz
THE PicoScope Automotive Authority
In North America