there are three things wrong with the d17. 1) the feul line (which has already been discussed) 2) the intake manifold and 3) the bottom end (which pete missed a major point). The intake manifold just sucks. for one, its made out of plastic and is very flimsy. for another, its a top mounted TB. you get a lot more air in the middle two cylinders than the outside two. that means that you get unequal pressure on the crank and, under boost, things will break more easily. also, the main problem with the bottom end, as pete said, is the internals are weaker than previous D series engines. but just as importantly, the rod/stroke ratio sucks *** for boost. its the same bore as the earlier Ds but it has a longer stroke to make the bigger displacement. the problem with this is that it puts more pressure outwards towards the head and bottom end. under boost the rods will be m ore succeptable to breakage than in a D series...and its worse that theyre weaker. theyre just not a good engine to boost and the amount of work you put into them to get them to run like a K...it will be cheaper to get a K.

 

i would be worrying about pistons and rods before a cam.... but thats just me... if you save for a k20 then some bolt ons... 100% more reliable. and more funner to drive...

 

more fun

honestly with all the time and money you will put into the d17 to get to the k20 standards it will be cheaper and easier to get a k20.