You can do all sorts! I'm currently in the process of fitting a hybrid turbo. Should be looking at 230bhp and 370ft/lb of torque once I'm done. That's on a diesel.
Money is all you need fella!
Normal, decent mods are:
Green panel filter;
PD160 air intake;
remap;
Front mount intercooler;
decent exhaust system
With that you should be seeing best part of 280ft/lb of torque and 180bhp.
Im getting my hybrid map done with RS on June 12th so I can let you know how it goes.