Dry kits are not for use on EFI cars, its best suited for carb'd engines that you can tune fuel in with just a screwdriver.
If you spray nitrous that far up the intake tube, you run a huge risk of puddling and blowing your intake to shreds. I have never heard of spraying before the MAF.
If youre going to do it, install the nozzle as close to the throttle body as you can get. If you have a tuner, richen the AF mix to accomodate the n2o.
I know someone with a firebird that thought he'd have fun and install a used dry kit onto his car.. within a few weeks he had backfired it and blown his filter and air meter to pieces, and within a few months the engine failed.
N2O can be extremely dangerous for your engine when you dont do it the right way. An untuned dry shot into the MAF, IMO, is a good example of the wrong way.