Im relatively new to turbos and have some questions regarding their power and maintence. What things would i need to buy to adjust the psi of the turbo? Also how do i keep my turbo in good working order and how can i measure its preformace to make sure its still runing smoothly. Thank you for answers.

Cars:
Volvo 1992 940 (wagon) Turbo

you can either purchase a manual boost controller or you can have your ecu programmed...as well you should buy a boost gauge with that...seeing your boost is the best indicator as to how well your turbo is running and will be your first line of defense when determining if there are any problems...

Yes make sure you install an aftermarket boost guage first though.