BTR starts with the basic NOS kit, which is a dry setup, with a TPS WOT switch,
and a electronic fuel enrichment module that taps into the intake air sensor
wire and the coolant wire - to fool the PCM into keeping the injectors open
longer. Then it adds propane as a fuel source to push it beyond the limits
of a dry only setup. Propane also has an octane rating of around 102.
Because propane pressure is limited to around 200psi, its upper limits as
a single stage HP source is around 200hp, so for an extra kick(and extra money), BTR has a gasoline stage add-on.
The basic NX setup is (someone correct me if I miss something) a wet
kit with a manual throttle WOT switch. The gasoline can be provided by tapping into the fuel plug on the intake, or a fuel cell with a pump to provide pressure.
Once you obtain either basic kit - NOS or NX, there is almost no limit
to your ability to customize or upgrade. You can even put a kit together
yourself and replicate what is available in kit form.
Tom uses the propane with the NOS kit, but propane could be just as easily
adapted to the NX kit. Buy a basic NX or NOS kit, then get a cheap propane tank and
some SS braided hose, a small solenoid, & jets.
Any of the electronic components of either system can be adapted to the
other. So if you have one system and want to add a different WOT switch or an enrichment
module - just let me know and I can tell you how to hook it up.