Bad surging on the bottle.
I checked my fuel pressure first and made sure I was getting good fuel pressure straight out of the rail. My FPSS has a rubber plug in the top that you can remove. Once you remove this plug there is a Hex screw in there. You turn it counter clockwise(I think) to lower the FPSS. I just had that same problem. Basically I kept lowering mine little by little until I got it to spray consistent. But like what was said earlier, you don't want to set it too low.
greg i have had the same issues (only at BMP ironically) when my bottle pressure was low due to low volume of nitrous. hope you get it worked out and let me know when you want to hit up BMP. love to see that beast down teh track
