Awesome project! Best way upgrade cp4 is to take 50d pump part number 0445010672. It allow you rise railpressure to 2200bar an it's capable around 500hp. You need just change highpressurelines from pump to rail or make shims between line and pump. I think US 535d is identific EURO spec 530d but you guys have 535d bigger injectors.
I have here in Finland f31 330d 190kw with wagner cooler, 3" turbo back exhaust, dpf/egr "swirl flaps" deleted, moded intake, stage 2 Snowperformance w/m with 100/175ml injectors. Tomorrow I'll install ported&polished exhaust manifold and Proturbo hybrid turbo, there is also 50d pump and 35d bigger injectors wating for install. Have them wait for spring that I got time to spend in dyno.
Sorry about bad language.