Is that piece which is used to flash ECM a one use only unit or can it be used several times?
Anyone know what the difference between stage 2 and stage 3 is?

 

HD Tool marries to the ECM, so it is Single-use, for all practical purposes. There are others that are usable on multiple bikes--at additional cost.
Stage I assumes stock Black injectors, SE air cleaner and SE/Kerker Touring mufflers.
Stage II assumes Orange Injectors, SE3 cam, SE Air Cleaner, SE/Kerker Touring pipes.
Stage III assumes higher (10.5:1? Don't remember for sure) compression with milled (but not ported) heads, pipes, and otherwise stock (if I remember right). Almost never installed.
Next up would be Stage II With Heads, which assumes everything in Stage II, plus SE heads. (9.5:1 CR).
Next would be the SE57 HO flash, which includes all the above, but with SE57 cam, and SE 43mm throttle body.


These flashes support from about 55 real-life horsepower all the way up to about 85 or a little better. (All the Evo EFI stockers that I've owned, worked on, or otherwise observed, were delivered with around 49-50 horsepower).

 

Thanks, interesting site you have, I'll have to spend some time reading there.