There are a whole host of engine management systems that will work on the SVX.

They include:

Electromotive TEC-II and TEC-III
Haltec
Motec
Microtec
Greddy E-manage
Dastek Unichip

Plus a great many more that are less well-known, like the
SDS shown in the link. Too bad it's quite slow compared to the more modern setups like the TEC.

My personal favorite for simple bolt-on tunability is the Unichip, though it's nowhere near as powerful as something like a TEC-III... you don't have to tune from scratch as with the standalone systems.