Don't forget the nitrous tune! And be sure you fuel and ignition system is sound - wires, coil, fuel pump & filter.
Plug gap should be between .030-.040, .035. usually works bests.
bottle heater - go with a pressure based control switch vs the more common temp based ones.
If you're going to the track they may also require a fire jacket so check on their rules for that and the blow down.
And as long as we're spending money look into a purge kit. Mostly looks cool but there are some practical uses such as venting pressure from the bottle and purging any gaseous nitrous in the line prior to a run.

DynoTune has a good selection of products for reasonable prices. I don't see them listing an EFI FPSS so you may want to ask them about it. Otherwise ebay to the rescue for a nice list of options.
The Blow down tube is the least expensive item on the list but here's a write up I did on making a Home Made Blow Down Tube