If it's the 2.0 Zetec, then there's the option of throttle bodies (probably cost upwards of 2 grand). That, combined with a nice free flowing exhaust will see it just shy of 200bhp.
Cheaper would be to dump in the 2.5 V6 from the Mondeo or another Cougar. Fantastic engines, and with the ST200 upper/lower inlets, throttle body and management will be, again, just shy of 200bhp. The ST200 engine (SEB) engines has a slightly higher compression ratio, so the standard SEA 170bhp one won't ever make exactly the same power.