Go for the Zex, there priced right and safe,you here just as many storeys of guys blowing up there cars using every type of Nitrous system on the market.
It's a Combination of bad gas,not enough octane,timing set to high,plugs were not cold enough, over revved it which cut out the fuel pump creating a lean condition.If you use the Zex system turn your timing down upgrade your fuel pump just to be safe and put in some 100 octane gas with colder plugs gapped at 40 thou and you'll be fine,if your car is a 93 don't use Nitrous at all,the pistons are not forged in 93.
Goodluck.....Oh ya it takes like 2 hours to put the Zex system in and like 4-6 for all the others.Plug and play.I talked to Zex before i bought mine and they said the 125 shot is safer then you think if done right and that the Mustang 5.0's will actually take 150 and 175 shot,but they don't tell people that because most people would use it on pump gas and boom...