It's on a handful of cars. The only things being perfected are CANbus systems so the dash, cruise, fuel computer etc all work as standard. Running the engine side of things is relatively straightforward
FYI it's £1040 for the ECU, you need an adapter as the GEN90 is Plug and play for a mk2, but a little different for a mk3. Once the kit it finalised you'll get all this as a 197/200 package. Don't just rely on the website though, speak to them, or me (I'm currently the only GEN90 trained external dealer for K-tec)
I run a GEN90 in my 172 demo car, and when that goes in a few weeks, the 197 I'll get to replace it will run one as soon as possible.