Water/Meth Flow vs. Water Flow Efficiency

[cewrx7r1]

Initially I was spraying water.
After calculating the flow rate that I needed, I would actually measure the amount of flow through the nozzle by:
(1) using a pressure regulator to apply the same pressure to the controller that I would be running.
(2) have the nozzle flow into an 1 gallon bottle for 1 minute.
(3) measure the collected water.
(4) then add in a little more flow because the nozzle was not under boost pressure when tested thus would flow a little more than when actually used.

When I went to water/meth a few months ago, I tested my new flow rate with water again.

I increased my boost pressure and decide to clean the jets and retest.
First at the old boost level. This time the test was done with 50/50 instead of water. To my surprise, the flow rate was noticeably higher than before.

Either:
(1) my system was flowing more because it is now broken in.
(2) water meth flows easier/more than water due to less density.
(3) or operator(me) error.

Has anyone notice this?