The NX kit is the best I've ever used. The provided jet sizes keep you plenty rich at all times. Wet is the only way to go. Use a wot switch, a fuel pressure switch, and an rpm window switch and you'll be virtually bulletproof. The general rule of thumb with nitrous applications is, most any engine can withstand a 50% hp boost from stock worth of nitrous. ie: 100hp zetec can take a 50 shot safely. I'm running a 75 shot with no trouble, it's tough to stick with 50 when 75 is just a wrench turn away.
One degree of timing should also be taken out for every 50 hp, but it's fairly safe to go a 50 shot without, 75 is pushing it, 100 will be trouble. The only way to retard the timing so far on our cars is with a chip. hope this helps, good luck
g