its not all that complicated.
you can do varies different setups depending on what you want to achieve. some do it just to lower EGT's (usually due to large amounts of fuel being poured in). it can be run via EGT sensor. boost sensor would be the most common. you can also do it via MAF sensor.
probably the biggest catch is lack of protection gear ie in case it fails. you may have to make it more basic (ie no pre turbo injection) to ensure reliability.
more so with small diesels as your on boost almost all the time.
most of the US setups tend to be either petrol or big diesel where your on boost (and use WI) only a small % of time. ie use it more like nitrous, that big hit when you stomp on the gas.
with the small diesels really need to either set it up to only work at max boost or run variable controller.
with basic boost switch setup you can get surging ie you hit cruise boost, WI kicks in more power so you take foot off gas to maintain steady speed. motor falls off boost WI turns off and you need to hit the gas hard to maintain speed. on/off right pain in the arse.
still biggest catch i think is the need for big tanks. not to bad if you have a flat deck, you can sneak 20+ litre water tank under it. very hard for a well side.
i should add that WI works in situations where intercooler do not work. ie going slow or in very hot conditions.
