Never been a fan of those air gap devices that are supposed to extend the spark duration - I always set my plugs with a gap right at the end.
I found one of those "catalyst" things in the fuel tank of my 350, put there by a previous owner, probably in an attempt to stop the rampant exhaust valve seat recession the bike was suffering from when I bought it. It has a couple of balls of Plutonium or Kryptonite or something similar in a little metal gauze cage. These things are so powerful that bike goes just as well with it sitting in a drawer in the garage!
I've also got one of those magnetic things that are fitted to the fuel line, designed to magically align the fuel molecules just before the go into the carburettor. I keep it stuck to an old tenon saw hanging up on the garage wall. Same thing for those; once the fuel has been aligned, you can remove it from the fuel line because what's left in the tank teaches new petrol how to behave. It's a miracle!

Built like a gun... could go BANG!