Why would it blow the intake welds? Surely the intake only sees normal boost pressure, the nos simply makes the mixture more dense......or am I being dense?

I think nos would be best used in small doses to bring the car on boost and then let the turbo do its bit....isn't this what Rod used it for as opposed to top end stuff...I.e. fill in the gaps? This way you can run bigger turbo for more boost and just cover the gap until the engine comes on cam and on full boost. David Vizard used to do thismonmthe a series back in the day.