It is turly 'plug & play' IF you can touch the top of your injectors. On the X5 they are right on top of the engine.
HOWEVER, on my '98 F-150, they're burried beneath the air intake plenum (12 bolts -3" long), and just about evey sensor connection known to man for engine operation. All together about 2 hrs twisting wrenches and a gasket (if you're not careful removing the plenum.).
Most of the Subaru's and older Ford Taurus' are a piece of cake. I haven't had any experience with any others.
Shortly tho, I will be installing a 4 cyl Full Flex Gold [
www.fullflexint.com] unit on my '01 BMW K1200LTC touring motorcycle.
(WHY a motorcycle -? you ask ?) Well, its just to prove that it can be done and that it will work on yet another 'older' engine.