The exhaust side of a turbo dosent care about exhaust pulses or pumping of the engine. It gives the hot exhaust gases somewhere to expand, and the rapid expansion is captured by the turbine. EGT retention is the name of the game on the exhaust side. The cold side(pressure side) is a pump. It can only create flow. It can’t create pressure as pressure is a measure of resistance. If the waste gate actuator is set for 20 PSI, and on the 6.5T you can achieve 20PSI manifold pressure, but on the 6.2 you can only achieve 18PSI. It boils down to intake manifold and cylinder head flow differences. The heads flow almost identical numbers to each other. The measurable difference is in the intake manifold flow numbers.
The unspoken of elephant in the room here is the air flow ability of the induction system. NO isn’t going to believe me on these number, but here are the number;550-about 600CFM. The factory air filter can only flow 500 CFM before it becomes a restriction.
If you don’t have the J code intake manifold, get one. Not knowing your ability, I would port match the intake manifold, port and polish the intake manifold and polish the intake plenum. Then, at least apply a DEI intake manifold heat shield to the bottom of the intake manifold. Keep your intake tubes the same size as your intake manifold inlet with smooth radius bends. Route the air filter out of the engine bay. Use the largest, highest flowing air filter you can. Wrap your intake tubes with a heat shield product. Stan’s headers makes a stainless steel header kit for the 6.2, I would buy them and wrap them with header wrap prior to install. Then have a ceramic coated, 3” exhaust system installed.
If you have an unlimited budget and just want to spend money on it, pull the heads and have the heads and J code intake manifold extrude honed. Install larger valves, Then port match the intake manifold and heads to each other and the headers to the heads to each other. Then do everything else recommended above.
But, typically, air flow is not an issue in terms of power production with a Diesel engine as a diesel can’t run to lean. Sure you can increase air flow as much as you want, you will be just moving more air out the exhaust pipe if you don’t have the fuel to take advantage of the increased air flow. A set of marine injectors and/or a turned up/recalibrated injection pump will net a noticeable power increase than increasing air flow.
Before anything is done, it’s highly recommended to install a set of gauges; EGT most importantly, before any power modifications are performed.