We can greatly increase the boost output from a factory turbo through ECU Tuning and Bolt-On modifications, but every turbocharger has a physical limit based on its size. When that limit is reached, it's time to go big.
Many people assume "Big Turbo" setups are for race cars only, but there are turbo upgrade options that preserve factory driveability and reliability. Depending on your vehicle, OEM Turbocharger Upgrades can provide a significant increase in power safely without the need to upgrade your engine's internal components.
A perfect example of an OEM upgrade is the IS38 Turbocharger, which comes on the Audi S3 and Volkswagen Golf R from the factory (Mk7.) This turbocharger can be easily installed on the VW GTI and Audi A4 and can be daily-driven, as long as the correct supporting modifications are also performed.
There are also excellent turbocharger upgrades that retain your factory turbo housing, making the installation process similar to replacing a factory turbo. PureTurbos offers kits that increase boost output by upgrading the turbocharger internals, such as the impeller, within the factory housing. This Stage 2 PureTurbo BMW 135i we built (pictured above) makes well over 500HP!
Of course, we're always willing and able to put together the biggest-frame, highest-output turbo kit you can afford. Our IS Works Audi TT drag car runs a GTX3071R Turbocharger and makes peak boost at 40PSI. But we believe in modifying safely. We have the experience to know exactly how much power a motor can handle and what supporting modifications are necessary to make sure that you will be able to enjoy your big-turbo build once its complete.