If plugs are going bad, he has a lot of tuning to do.
They should be fine for many years.
The JET module (that I wrote the installation manual for back in summer 2000) does not retard timing. It ties into the MAP and TPS signals and only effects part throttle performance. These sensors are not used at WOT.
You must use a wet kit.
I contributed to the NOS article in
www.cruiserquarterly.com as well as the install guide at
www.ptdiy.net
That guide should answer your questions.