I simply stated that I have rebuilt the stock engine 4 times as a show of how much TIME and MONEY I have spent RESEARCHING the best type of nitrous kit for the stock motor and where it's limitations are. Have you done such?
... I tested wet kits to start with and found that they are a complete waste of time on the 16v zetec. The intake manifold allows the air/fuel mixture to puddle in it causing a lean condition and allowing the engine to detonate. (verified via wideband O2 sensor) The only way to use a wet kit on the 16v zetec would be to design a new intake manifold that did not have the gooseneck in it. (I have done this)
...The only sort of nitrous kit that can be safely used is either a dry kit that tickles the stock injectors to inject more fuel or to setup your own direct port system that injects fuel AFTER the gooseneck. Either case requires that you have ample fuel supply and the kit be properly installed per the manufacturers directions.
...Injecting nitrous without extra fuel WILL destroy your engine. Please insure you use a kit that will provide additional fuel.

95 Contour, Custom EVO bodykit, 2.0l, PNP Focus head, Stage 2 cams, Je pistons, Eagle rods, 4in1header, 2.5" header back exhaust(complete stainless), D P nitrous, ram air intake, 10mm wires, flamethrower.