75 shot
You can get by with a single fogger at the throttle body and a 75 shot. 90 occasionally. I've run 75 shot forever, and fifty on the engine fro some time before that.
90 I use very rarely (probably 10 times over the years) I don't have any confidence that a 90 will last for any great legnth of time like a 75 or 50 shot would. My bud lifted his headgasket detonating on a 90 shot running almost an identical system setup as mine. It was funny, I laughed---he found no humoor in the situation whatsoever. So unless I REALLY want to win, I don't use the 90. As I near 150,000 miles on the engine and look to tear into it anyway for inspection I may use 90 more frequently to see if I can blow it up and use it as an excuse for a turbo conversion.
You need some of the stuff like James states as you near 100hp, and unless you are really going to get serious about the dragging and are going into the engine regularly for inspections, I'd stick to 75 or below HP.
I didn't like how hard the hit came from six nozzles in the manifold, I perfer the softer hit from mounting the fogger in the throttle body or rubber boot in front of it. Easier on the driveline. I've only replaced one driveshaft and the halfshafts, and they were suspect when I bought the car with 98,000 on it!