Have you re-newed some of the crispy wires and connections in the engine bay ?
Check your connector from the crankshaft sensor to your ECU. This is on top of the engine on the right hand side.
If you have re-newed this connector, this will be your problem.
All GTA Turbos were wired wrong in the factory. There are two wires (a red and a white) . If you connect red to red and white to white, you car will never start. But if you put
red to white, this is the way it will work.
You can obtain a copy of the wiring diagram from John Sweet or if hasn't got one left, give me a ring on 01492 533430, and I'll do you a copy of mine.