Assuming you are talking about a 7.3L Powerstroke diesel engine, there are a few ways to increase boost pressure. One way is to install a larger turbocharger. This will provide more air flow and therefore more boost. Another way is to increase the size of the intercooler. This will help to cool the air coming from the turbocharger before it enters the engine, allowing for more dense air and more boost. Finally, you can also adjust the Wastegate actuator rod to increase boost pressure.