Well...

The top speed of the stock SiR is around 210 km/h or so.

If that's not enough for you, you can go the full exhaust route (get surplus headers), get engine management (andaming SAFC na available) and maybe a set of secondhand cams. Each job can be done quickly (in a day or so) so you won't have the car off the road for too long. And get some good brake pads. At the end of that, your car should be capable of hitting 220-230 km/h, and you won't have spent more than 50k pesos.

Any turbo set-up will take a lot of time and tuning. You'll have to schedule a month at least, or up to two or three if it's a complicated custom job (especially if you really want 250 whp).