honestly, the only thing to get the cummins turbo diesel 5.9 I6 engine to get that power was boost fooler, mbc, fuel injectors, exhaust, and there are people pushing over 400whp and 780tq @ wheels ... with just above mods.. but the turbo dies shortly at those levels, but a $1200 turbo replacement will net me another 10 years of fun ...
that is in manual... in my case (auto) i'd have to upgrade torq converter and valve body (another $2k) and i will be at those levels without any worry of breaking other than the driveshaft
-E