The Volvo modular in the t5 has forged steel internals. Definitely capable of a lot more power. Depending on how boost is managed already, it may be as simple as a flash tune and a few dyno pulls. If not, you may need a boost controller. Any amount of boost you add will start requiring supporting mods, larger intercooler, better flowing fuel injectors, a higher output fuel pump... etc. I think the best place to start would be looking for a performance shop that specializes in volvo, or at least a forum or somewhere that people have experience with your specific car. Not trying to redirect you somewhere else, just saying that it varies widely, and it would be best to talk to someone who knows more about your car specifically.