This is a common problem with the Corrado G60s, and I went through the above diagnostics without finding a solution. There is

a TSB out on this that recommends cutting a wire to the ECU. I don't like cutting wires, so I never did that.

However, about a year later, I finally resolved the problem.

The symptoms of a "hard starting" G60 is that you start the car, and it sputters a bit, then dies. Usually after the 3rd start of so the car will run, but will stall out when driven. Over time, the hard starting got worse. First I needed two tries, then three, and so on. Only when the car is warmed up, will it drive normally. Once car cools down again, the problem re-occurs. Needles to say, this was driving me crazy.

The solution was extremely simple...fuel filter. After I installed the supposedly "unservicable" fuel filter during the 120 000 miles service, the car finally starts up the first time and keeps on running. I change the fuel filter, which is near the passenger right wheel, every 60 000 miles, but you may need to do it more frequently. You'll need to get a new set of hose clamps, but the rest is trivial.

If that and the above does not solve your problem you may want to check out the corrado-club archives. There is one under "Fixing a Bad G60 Idle" that mentions a bad ECU frame ground contact. Go figure.