You can change your injectors, but it needs careful consideration.
A few years ago Severn Valley Motorsport did exactly the same thing, and they used Bosch K-Jetronic injectors from a Saab 900 Turbo (a 4 cylinder 1985cc with 155bhp/235Nm). Other turbocharged 4 cylinder cars that use the Bosch K-Jetronic or KE-Jetronic fuel injection system include, the Volvo 240 Turbo (a 4 cylinder 2127cc with 155bhp/240Nm) and the Lotus Esprit Turbo (a 4 cylinder 2174cc with 218bhp/270Nm).
However, it is probably easier and more cost-efficient to simply fit a 5th injector, controlled by an ERL MF2, with either 2D or 3D fuel mapping.

If you need anymore help, just PM me.
Take care,
Dean