Having after market fuel pumps for nitrous kits is a good idea.  You can put great stress on your gas system when driving hard.  The added stress can put a shorter lived life on stock gas systems.  

The reason why people get upgraded gas pumps for nitrous kits, turbo kits, even N/A builds is simple.  Your stock system is only set up to handle the gas needs for a stock motor.  Nitrous kits, turbos, and N/A builds will use up gas.  This creates a greater stress on the pump itself, and can cause failure, over heating, or inconsistent pumping.  All of which are a danger to your motor.

Nitrous kits need the extra gas when being used.  Nitrous kits have new technology that only allow them to activate at WOT.  When nitrous kits are activated at WOT they run in open loop on your ECU.  What open loop is, is when your gas injectors are just dumping the largest amount of gas that they can into the combustion chamber.  The nitrous mixes with the gas to create that highly oxidative bang that you get from nitrous.  The kits can put such a strain on stock pumps because of this, it leads to failure, and possibly running lean.

• After market gas pumps
• Protect your engine
• Keep your engine from running lean

When you run lean, your motor is not using the safe amount of gas your engine needs.  Especially when using nitrous kits, your engine runs at a higher engine temperature.  The gas in the chamber burns up quicker than it should and explodes before the piston reaches TDC.  This can ultimately lead to the end of your engine.  

An after market gas pump can offer you protection from all these issues, when using nitrous kits, turbos, or N/A builds.  Nitrous kits are easier to install than turbo's or complete N/A builds.  Most nitrous kits can be bolted right on and ready to be used in a few hours.  The pumps can help to protect your stock engine block and gas system.