I'm partial to Nitrous Express. I just like the quality of their products and their customer service is good. I have their billet crossbar kit.
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Lastly, I'd invest in a good Programer, bottle warmer, dual bank A/F gauge, and retard switch. The programmer will allow you to ramp the shot so you're not hitting the motor all at once. This will help to keep it alive longer. You can also delay the shot, which is nice if traction is an issue.
The bottle warmer will help you to keep a consistent PSI. And the retard switch is pretty self explanatory.
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