Refer to the thread by Brett in installing water/meth to his C6.

Due to the MAF being only a few inches from the throttlebody and the water/meth being installed in that narrow couple between the two there is a chance when w/meth is being sprayed the fluid can get onto the exposed sensors of the MAF and cause ill engine functioning and trick other functions of car to trip false DTC error codes as shown ( review the color codes in DTC snapshot.

The nozzle that comes with the w/meth sprays in 360 degrees, review the image closely to see that.

Notice the collected OBD-II data where w/meth came on and the MAF output frequency is wacko and not normal as w/meth sprayed fluid onto MAF exposed sensors

We made up a testrig and made a top to nozzle that causes the spray to only spray into the intake manifold and away from the MAF

Other solutions could be mounting MAF further away from the throttleboy, finding a uni-directional nozzle or as we did make one that you could done with about anything from a piece of hose that is capped and cutting a V angle to force spray into intake.
V cut must by wide angle so fluid maintains a mist pattern.

Also nozzles for N20 (NOS) are made that are uni-directional that would work

Note: I used on purpose a lower PSI pump so that fluid would be seen better as if using the w/meth pump water would not be seen as it would be a mist at 150 PSI where pump used for test was only about 30-50 PSI