zex managment unit clicking?

I was on the highway and I sprayed to merg cuz a guy was being a dick. When I engaged the system and floored it, I heard a rapid clicking sound but the system worked. At first I though it was my MSD Digital 6 retarting the timing but it only happened at WOT when the kit sprayed. Kit is a Zex wet kit on a B18A motor, when I opened my bottle the gauge read 900psi, Im gonna weigh it tomarrow to see how much N2O I have left but I shouldnt be out. When I installed the kit and used it I thought maybe something was wrong with it cuz it didnt perform like I thought it would. In a 90 teg with I/H/E and a 55 shot I ran a best of a 16.5. The car does pick up when it sprayes but I dont think it does like it should

EDIT I weighed the bottle and it was 16 lbs. empty id 14.6lbs so i have a little over a pound of N2O, does it click because its

900 psi is a little low isnt it, from what i remember on my old setup it should be somewhere around 1200-1400 psi, anyway think the clicking has something to do with the solenoids, i would check those, and also the purple box.

the solinoids are inside the purple box, so are the fuel enrichment components