Hi William,

Happy New Year to you too 

You 'need' two channels.  This is essential to do action/reaction, input/output tests.

Four channels can save time in many situations and can reduce the number of captures needed to identify an issue.  Also a 'need' if you do any teaching so you can show students more interactions.

IMHO, if you think you need 8 channels, your diagnostic strategy is probably in need of refinement.  8 channels also clutters up the screen and would likely degrade performance.  Four channels with the incredible detail of Pico would be all that is needed.

PicoScope can only run one scope.  You will not be able to run two four channel scopes at the same time, as the software can only communicate with one at a time.  Even if you wrote your own software to accomplish this, it would not be an 8 channel scope.  It would be two, four channel scopes.  They would not be synchronized and would sample at different times.  This means that channel interrelationships between scopes would not be in the same time frame.

My kinda guy  

Yeah, if you were to sync each scope to the same signal then they would be related captures but still not in the same time frame.  Each sync event would be a different one.  Example:

Scope A triggers on injector firing.  Scope B triggers on the same injector but a different event.  And so on.  The captures from each scope will still be in a different time frame from a different trigger event.  This is how the driver works.  It can only run one scope at a time.  They would take turns.