There are plenty of threads on this forum about bumping up power. Do a search but you basically have five choices.
1) Mosselman or TurboTechnics Twin Turbo units. Mosselman kits run around $6500 and the Turbotechnics kits have been on firesale lately for about 2500US out of England [not sure about shipping. Should give 300HP at the CRANKSHAFT
2) Roll your own turbo system. Doable but requires more engineering and “trial and error” Power depends on the way you build the system
3) Rebuild the motor with lightweight pistons, conrods, balance the crankshaft, port and polish, bump up the injectors, fuel pump etc. This will give about 240-250HP at the CRANKSHAFT. Cost will be about $5000-$7500 by the time you are done.
4) Transplant a M119 motor out of a 400E or 500E [or 500SL or 500SE]. That will require some engineering to make everything fit and all the wiring CAN BUS changes, labor and cost of motor/tranny, driveshaft. Expect about $7000+. [The motor/tranny in good shape will be $4000 IF it doesn’t need any work.]
5) Trade your car for a 400E or 500E and you will have factory 275-325HP out of the box.