yes yes and yes.
All depends on what you want and how much you want to pay.
I can get cheap guages but to be honest your better off spending more money for and expensive one I've seen both and with the more expenisve models you get everything you need with them generally.
BOV's I can get cheap or expensive however if your looking to not destroy your turbo highly suggest going with expensive. The cheap ones tend to all of a sudden not work and you get compressor surge and bang there goes your turbo all over a couple hundred dollars.
Boost controller and turbo timers depending on model usually set you back at least a couple hundred each.
Turbo stuff is not cheap and it pays to spend more for quality gear.