synthetic oil
add oil cooler
check/new timing belt
new spark plug wires / plugs
aftermarket anti-sway bar(s), if you don't have any.
this would also mean a new upper front strut tower brace
lower front strut tower brace
rear upper strut tower brace
"stock item only goes to 8000rpm."
i get the distinct feeling this is wrong.
it's a gut feeling type thing.
best, check a loaded sprinter and see all the cool shit.