Actually the engines are very sensitive to nitrous,
any detonation and the pistons (among other things) will shatter like glass.
The Zetec has hypereutectic pistons, which are the worst pistons to run with nitrous.
Anybody with any automotive knowledge will tell you not to run nitrous (of any size or type kit) on an engine with hypereutectic pistons.
But if this is taken into account it can be tuned around.
I have run 55HP to 75HP shot for 3 years with no problems at all.
I have even run a 100HP & 125HP shot for a few runs at the track.
